Merge pull request #847 from 0xProject/refactor/contracts/simplify-forwarder

Refactor forwarding contract architecture, remove batch functions

33 files changed, 1740 insertions, 1890 deletions

diff --git a/packages/contracts/src/2.0.0/forwarder/Forwarder.sol b/packages/contracts/src/2.0.0/forwarder/Forwarder.sol
index 546e7f22c..5b88b05b1 100644
--- a/packages/contracts/src/2.0.0/forwarder/Forwarder.sol
+++ b/packages/contracts/src/2.0.0/forwarder/Forwarder.sol
@@ -19,20 +19,19 @@
 pragma solidity 0.4.24;
 pragma experimental ABIEncoderV2;
 
-import "./MixinFees.sol";
+import "./MixinWeth.sol";
 import "./MixinForwarderCore.sol";
-import "./MixinConstants.sol";
-import "./MixinMarketBuyZrx.sol";
-import "./MixinExpectedResults.sol";
-import "./MixinTransfer.sol";
+import "./libs/LibConstants.sol";
+import "./MixinAssets.sol";
+import "./MixinExchangeWrapper.sol";
 
 
+// solhint-disable no-empty-blocks
 contract Forwarder is
-    MixinConstants,
-    MixinExpectedResults,
-    MixinFees,
-    MixinMarketBuyZrx,
-    MixinTransfer,
+    LibConstants,
+    MixinWeth,
+    MixinAssets,
+    MixinExchangeWrapper,
     MixinForwarderCore
 {
 
@@ -44,7 +43,7 @@ contract Forwarder is
         bytes memory _wethAssetData
     )
         public
-        MixinConstants(
+        LibConstants(
             _exchange,
             _etherToken,
             _zrxToken,
diff --git a/packages/contracts/src/2.0.0/forwarder/MixinTransfer.sol b/packages/contracts/src/2.0.0/forwarder/MixinAssets.sol
index bebfc976b..5cf5f831b 100644
--- a/packages/contracts/src/2.0.0/forwarder/MixinTransfer.sol
+++ b/packages/contracts/src/2.0.0/forwarder/MixinAssets.sol
@@ -19,58 +19,78 @@
 pragma solidity 0.4.24;
 
 import "../utils/LibBytes/LibBytes.sol";
+import "../utils/Ownable/Ownable.sol";
+import "../tokens/ERC20Token/IERC20Token.sol";
 import "../tokens/ERC721Token/IERC721Token.sol";
-import "./mixins/MTransfer.sol";
+import "./libs/LibConstants.sol";
+import "./mixins/MAssets.sol";
 
 
-contract MixinTransfer is
-    MTransfer
+contract MixinAssets is
+    Ownable,
+    LibConstants,
+    MAssets
 {
 
     using LibBytes for bytes;
 
     bytes4 constant internal ERC20_TRANSFER_SELECTOR = bytes4(keccak256("transfer(address,uint256)"));
-    bytes4 constant internal ERC721_RECEIVED = bytes4(keccak256("onERC721Received(address,uint256,bytes)"));
-    bytes4 constant internal ERC721_RECEIVED_OPERATOR = bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"));
 
-    function onERC721Received(
-        address,
-        uint256,
-        bytes memory
+    /// @dev Withdraws ERC20 tokens from this contract. The contract requires a ZRX balance in order to 
+    ///      function optimally, and this function allows the ZRX to be withdrawn by owner. It may also be
+    ///      used to withdraw tokens that were accidentally sent to this contract.
+    /// @param token Address of ERC20 token to withdraw.
+    /// @param amount Amount of ERC20 token to withdraw.
+    function withdrawERC20(
+        address token,
+        uint256 amount
     )
-        public
-        pure
-        returns(bytes4)
+        external
+        onlyOwner
     {
-        return ERC721_RECEIVED;
+        require(
+            IERC20Token(token).transfer(msg.sender, amount),
+            "WITHDRAWAL_FAILED"
+        );
     }
 
-    function onERC721Received(
-        address,
-        address,
-        uint256,
-        bytes memory
+    /// @dev Transfers given amount of asset to sender.
+    /// @param assetData Byte array encoded for the respective asset proxy.
+    /// @param amount Amount of asset to transfer to sender.
+    function transferPurchasedAssetToSender(
+        bytes memory assetData,
+        uint256 amount
     )
-        public
-        pure
-        returns(bytes4)
+        internal
     {
-        return ERC721_RECEIVED_OPERATOR;
+        bytes4 proxyId = assetData.readBytes4(0);
+
+        if (proxyId == ERC20_DATA_ID) {
+            transferERC20Token(assetData, amount);
+        } else if (proxyId == ERC721_DATA_ID) {
+            transferERC721Token(assetData, amount);
+        } else {
+            revert("UNSUPPORTED_TOKEN_PROXY");
+        }
     }
 
+    /// @dev Decodes ERC20 assetData and transfers given amount to sender.
+    /// @param assetData Byte array encoded for the respective asset proxy.
+    /// @param amount Amount of asset to transfer to sender.
     function transferERC20Token(
-        address token,
-        address to,
+        bytes memory assetData,
         uint256 amount
     )
         internal
     {
+        address token = assetData.readAddress(16);
+
         // Transfer tokens.
         // We do a raw call so we can check the success separate
         // from the return data.
         bool success = token.call(abi.encodeWithSelector(
             ERC20_TRANSFER_SELECTOR,
-            to,
+            msg.sender,
             amount
         ));
         require(
@@ -100,18 +120,27 @@ contract MixinTransfer is
         );
     }
 
+    /// @dev Decodes ERC721 assetData and transfers given amount to sender.
+    /// @param assetData Byte array encoded for the respective asset proxy.
+    /// @param amount Amount of asset to transfer to sender.
     function transferERC721Token(
         bytes memory assetData,
-        address to
+        uint256 amount
     )
         internal
     {
+        require(
+            amount == 1,
+            "INVALID_AMOUNT"
+        );
         // Decode asset data.
         address token = assetData.readAddress(16);
         uint256 tokenId = assetData.readUint256(36);
+
+        // Perform transfer.
         IERC721Token(token).transferFrom(
             address(this),
-            to,
+            msg.sender,
             tokenId
         );
     }
diff --git a/packages/contracts/src/2.0.0/forwarder/MixinErrorMessages.sol b/packages/contracts/src/2.0.0/forwarder/MixinErrorMessages.sol
deleted file mode 100644
index 1b3e3f488..000000000
--- a/packages/contracts/src/2.0.0/forwarder/MixinErrorMessages.sol
+++ /dev/null
@@ -1,35 +0,0 @@
-/*
-
-  Copyright 2018 ZeroEx Intl.
-
-  Licensed under the Apache License, Version 2.0 (the "License");
-  you may not use this file except in compliance with the License.
-  You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-  Unless required by applicable law or agreed to in writing, software
-  distributed under the License is distributed on an "AS IS" BASIS,
-  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-  See the License for the specific language governing permissions and
-  limitations under the License.
-
-*/
-
-// solhint-disable
-pragma solidity 0.4.24;
-
-
-/// This contract is intended to serve as a reference, but is not actually used for efficiency reasons.
-contract MixinErrorMessages {
-    string constant VALUE_GREATER_THAN_ZERO = "VALUE_GREATER_THAN_ZERO";
-    string constant FEE_PROPORTION_TOO_LARGE = "FEE_PROPORTION_TOO_LARGE";
-    string constant TAKER_ASSET_ZRX_REQUIRED = "TAKER_ASSET_ZRX_REQUIRED";
-    string constant TAKER_ASSET_WETH_REQUIRED = "TAKER_ASSET_WETH_REQUIRED";
-    string constant SAME_ASSET_TYPE_REQUIRED = "SAME_ASSET_TYPE_REQUIRED";
-    string constant UNACCEPTABLE_THRESHOLD = "UNACCEPTABLE_THRESHOLD";
-    string constant UNSUPPORTED_TOKEN_PROXY = "UNSUPPORTED_TOKEN_PROXY";
-    string constant ASSET_AMOUNT_MATCH_ORDER_SIZE = "ASSET_AMOUNT_MUST_MATCH_ORDER_SIZE";
-    string constant DEFAULT_FUNCTION_WETH_CONTRACT_ONLY = "DEFAULT_FUNCTION_WETH_CONTRACT_ONLY";
-    string constant INVALID_MSG_VALUE = "INVALID_MSG_VALUE";
-}
diff --git a/packages/contracts/src/2.0.0/forwarder/MixinExchangeWrapper.sol b/packages/contracts/src/2.0.0/forwarder/MixinExchangeWrapper.sol
new file mode 100644
index 000000000..f3aa483c5
--- /dev/null
+++ b/packages/contracts/src/2.0.0/forwarder/MixinExchangeWrapper.sol
@@ -0,0 +1,253 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity 0.4.24;
+pragma experimental ABIEncoderV2;
+
+import "./libs/LibConstants.sol";
+import "./mixins/MExchangeWrapper.sol";
+import "../protocol/Exchange/libs/LibAbiEncoder.sol";
+import "../protocol/Exchange/libs/LibOrder.sol";
+import "../protocol/Exchange/libs/LibFillResults.sol";
+import "../protocol/Exchange/libs/LibMath.sol";
+
+
+contract MixinExchangeWrapper is
+    LibAbiEncoder,
+    LibFillResults,
+    LibMath,
+    LibConstants,
+    MExchangeWrapper
+{
+
+    /// @dev Fills the input order.
+    ///      Returns false if the transaction would otherwise revert.
+    /// @param order Order struct containing order specifications.
+    /// @param takerAssetFillAmount Desired amount of takerAsset to sell.
+    /// @param signature Proof that order has been created by maker.
+    /// @return Amounts filled and fees paid by maker and taker.
+    function fillOrderNoThrow(
+        LibOrder.Order memory order,
+        uint256 takerAssetFillAmount,
+        bytes memory signature
+    )
+        internal
+        returns (FillResults memory fillResults)
+    {
+        // ABI encode calldata for `fillOrder`
+        bytes memory fillOrderCalldata = abiEncodeFillOrder(
+            order,
+            takerAssetFillAmount,
+            signature
+        );
+
+        address exchange = address(EXCHANGE);
+
+        // Call `fillOrder` and handle any exceptions gracefully
+        assembly {
+            let success := call(
+                gas,                                // forward all gas, TODO: look into gas consumption of assert/throw
+                exchange,                           // call address of Exchange contract
+                0,                                  // transfer 0 wei
+                add(fillOrderCalldata, 32),         // pointer to start of input (skip array length in first 32 bytes)
+                mload(fillOrderCalldata),           // length of input
+                fillOrderCalldata,                  // write output over input
+                128                                 // output size is 128 bytes
+            )
+            switch success
+            case 0 {
+                mstore(fillResults, 0)
+                mstore(add(fillResults, 32), 0)
+                mstore(add(fillResults, 64), 0)
+                mstore(add(fillResults, 96), 0)
+            }
+            case 1 {
+                mstore(fillResults, mload(fillOrderCalldata))
+                mstore(add(fillResults, 32), mload(add(fillOrderCalldata, 32)))
+                mstore(add(fillResults, 64), mload(add(fillOrderCalldata, 64)))
+                mstore(add(fillResults, 96), mload(add(fillOrderCalldata, 96)))
+            }
+        }
+        return fillResults;
+    }
+
+    /// @dev Synchronously executes multiple calls of fillOrder until total amount of WETH has been sold by taker.
+    ///      Returns false if the transaction would otherwise revert.
+    /// @param orders Array of order specifications.
+    /// @param wethSellAmount Desired amount of WETH to sell.
+    /// @param signatures Proofs that orders have been signed by makers.
+    /// @return Amounts filled and fees paid by makers and taker.
+    function marketSellWeth(
+        LibOrder.Order[] memory orders,
+        uint256 wethSellAmount,
+        bytes[] memory signatures
+    )
+        internal
+        returns (FillResults memory totalFillResults)
+    {
+        bytes memory makerAssetData = orders[0].makerAssetData;
+        bytes memory wethAssetData = WETH_ASSET_DATA;
+
+        uint256 ordersLength = orders.length;
+        for (uint256 i = 0; i != ordersLength; i++) {
+
+            // We assume that asset being bought by taker is the same for each order.
+            // We assume that asset being sold by taker is WETH for each order.
+            orders[i].makerAssetData = makerAssetData;
+            orders[i].takerAssetData = wethAssetData;
+
+            // Calculate the remaining amount of WETH to sell
+            uint256 remainingTakerAssetFillAmount = safeSub(wethSellAmount, totalFillResults.takerAssetFilledAmount);
+
+            // Attempt to sell the remaining amount of WETH
+            FillResults memory singleFillResults = fillOrderNoThrow(
+                orders[i],
+                remainingTakerAssetFillAmount,
+                signatures[i]
+            );
+
+            // Update amounts filled and fees paid by maker and taker
+            addFillResults(totalFillResults, singleFillResults);
+
+            // Stop execution if the entire amount of takerAsset has been sold
+            if (totalFillResults.takerAssetFilledAmount >= wethSellAmount) {
+                break;
+            }
+        }
+        return totalFillResults;
+    }
+
+    /// @dev Synchronously executes multiple fill orders in a single transaction until total amount is bought by taker.
+    ///      Returns false if the transaction would otherwise revert.
+    ///      The asset being sold by taker must always be WETH.
+    /// @param orders Array of order specifications.
+    /// @param makerAssetFillAmount Desired amount of makerAsset to buy.
+    /// @param signatures Proofs that orders have been signed by makers.
+    /// @return Amounts filled and fees paid by makers and taker.
+    function marketBuyWithWeth(
+        LibOrder.Order[] memory orders,
+        uint256 makerAssetFillAmount,
+        bytes[] memory signatures
+    )
+        internal
+        returns (FillResults memory totalFillResults)
+    {
+        bytes memory makerAssetData = orders[0].makerAssetData;
+        bytes memory wethAssetData = WETH_ASSET_DATA;
+
+        uint256 ordersLength = orders.length;
+        for (uint256 i = 0; i != ordersLength; i++) {
+
+            // We assume that asset being bought by taker is the same for each order.
+            // We assume that asset being sold by taker is WETH for each order.
+            orders[i].makerAssetData = makerAssetData;
+            orders[i].takerAssetData = wethAssetData;
+
+            // Calculate the remaining amount of makerAsset to buy
+            uint256 remainingMakerAssetFillAmount = safeSub(makerAssetFillAmount, totalFillResults.makerAssetFilledAmount);
+
+            // Convert the remaining amount of makerAsset to buy into remaining amount
+            // of takerAsset to sell, assuming entire amount can be sold in the current order
+            uint256 remainingTakerAssetFillAmount = getPartialAmount(
+                orders[i].takerAssetAmount,
+                orders[i].makerAssetAmount,
+                remainingMakerAssetFillAmount
+            );
+
+            // Attempt to sell the remaining amount of takerAsset
+            FillResults memory singleFillResults = fillOrderNoThrow(
+                orders[i],
+                remainingTakerAssetFillAmount,
+                signatures[i]
+            );
+
+            // Update amounts filled and fees paid by maker and taker
+            addFillResults(totalFillResults, singleFillResults);
+
+            // Stop execution if the entire amount of makerAsset has been bought
+            if (totalFillResults.makerAssetFilledAmount >= makerAssetFillAmount) {
+                break;
+            }
+        }
+        return totalFillResults;
+    }
+
+    /// @dev Buys zrxBuyAmount of ZRX fee tokens, taking into account ZRX fees for each order. This will guarantee
+    ///      that at least zrxBuyAmount of ZRX is purchased (sometimes slightly over due to rounding issues).
+    ///      It is possible that a request to buy 200 ZRX will require purchasing 202 ZRX
+    ///      as 2 ZRX is required to purchase the 200 ZRX fee tokens. This guarantees at least 200 ZRX for future purchases.
+    ///      The asset being sold by taker must always be WETH. 
+    /// @param orders Array of order specifications containing ZRX as makerAsset and WETH as takerAsset.
+    /// @param zrxBuyAmount Desired amount of ZRX to buy.
+    /// @param signatures Proofs that orders have been created by makers.
+    /// @return totalFillResults Amounts filled and fees paid by maker and taker.
+    function marketBuyZrxWithWeth(
+        LibOrder.Order[] memory orders,
+        uint256 zrxBuyAmount,
+        bytes[] memory signatures
+    )
+        internal
+        returns (FillResults memory totalFillResults)
+    {
+        // Do nothing if zrxBuyAmount == 0
+        if (zrxBuyAmount == 0) {
+            return totalFillResults;
+        }
+
+        bytes memory zrxAssetData = ZRX_ASSET_DATA;
+        bytes memory wethAssetData = WETH_ASSET_DATA;
+        uint256 zrxPurchased = 0;
+
+        uint256 ordersLength = orders.length;
+        for (uint256 i = 0; i != ordersLength; i++) {
+
+            // All of these are ZRX/WETH, so we can drop the respective assetData from calldata.
+            orders[i].makerAssetData = zrxAssetData;
+            orders[i].takerAssetData = wethAssetData;
+
+            // Calculate the remaining amount of ZRX to buy.
+            uint256 remainingZrxBuyAmount = safeSub(zrxBuyAmount, zrxPurchased);
+
+            // Convert the remaining amount of ZRX to buy into remaining amount
+            // of WETH to sell, assuming entire amount can be sold in the current order.
+            uint256 remainingWethSellAmount = getPartialAmount(
+                orders[i].takerAssetAmount,
+                safeSub(orders[i].makerAssetAmount, orders[i].takerFee),  // our exchange rate after fees 
+                remainingZrxBuyAmount
+            );
+
+            // Attempt to sell the remaining amount of WETH.
+            FillResults memory singleFillResult = fillOrderNoThrow(
+                orders[i],
+                safeAdd(remainingWethSellAmount, 1),  // we add 1 wei to the fill amount to make up for rounding errors
+                signatures[i]
+            );
+
+            // Update amounts filled and fees paid by maker and taker.
+            addFillResults(totalFillResults, singleFillResult);
+            zrxPurchased = safeSub(totalFillResults.makerAssetFilledAmount, totalFillResults.takerFeePaid);
+
+            // Stop execution if the entire amount of ZRX has been bought.
+            if (zrxPurchased >= zrxBuyAmount) {
+                break;
+            }
+        }
+
+        return totalFillResults;
+    }
+}
diff --git a/packages/contracts/src/2.0.0/forwarder/MixinExpectedResults.sol b/packages/contracts/src/2.0.0/forwarder/MixinExpectedResults.sol
deleted file mode 100644
index a575c9675..000000000
--- a/packages/contracts/src/2.0.0/forwarder/MixinExpectedResults.sol
+++ /dev/null
@@ -1,161 +0,0 @@
-/*
-
-  Copyright 2018 ZeroEx Intl.
-
-  Licensed under the Apache License, Version 2.0 (the "License");
-  you may not use this file except in compliance with the License.
-  You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-  Unless required by applicable law or agreed to in writing, software
-  distributed under the License is distributed on an "AS IS" BASIS,
-  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-  See the License for the specific language governing permissions and
-  limitations under the License.
-
-*/
-
-pragma solidity 0.4.24;
-pragma experimental ABIEncoderV2;
-
-import "../utils/LibBytes/LibBytes.sol";
-import "../protocol/Exchange/libs/LibFillResults.sol";
-import "../protocol/Exchange/libs/LibMath.sol";
-import "../protocol/Exchange/libs/LibOrder.sol";
-import "./mixins/MConstants.sol";
-import "./mixins/MExpectedResults.sol";
-
-
-contract MixinExpectedResults is
-    LibMath,
-    LibFillResults,
-    MConstants,
-    MExpectedResults
-{
-
-    /// @dev Calculates a total FillResults for buying makerAssetFillAmount over all orders.
-    ///      Including the fees required to be paid. 
-    /// @param orders An array of Order struct containing order specifications.
-    /// @param makerAssetFillAmount A number representing the amount of this order to fill.
-    /// @return totalFillResults Amounts filled and fees paid by maker and taker.
-    function calculateMarketBuyResults(
-        LibOrder.Order[] memory orders,
-        uint256 makerAssetFillAmount
-    )
-        public
-        view
-        returns (FillResults memory totalFillResults)
-    {
-        for (uint256 i = 0; i < orders.length; i++) {
-            uint256 remainingMakerAssetFillAmount = safeSub(makerAssetFillAmount, totalFillResults.makerAssetFilledAmount);
-            uint256 remainingTakerAssetFillAmount = getPartialAmount(
-                orders[i].takerAssetAmount,
-                orders[i].makerAssetAmount,
-                remainingMakerAssetFillAmount
-            );
-            FillResults memory singleFillResult = calculateFillResults(orders[i], remainingTakerAssetFillAmount);
-            addFillResults(totalFillResults, singleFillResult);
-            if (totalFillResults.makerAssetFilledAmount == makerAssetFillAmount) {
-                break;
-            }
-        }
-        return totalFillResults;
-    }
-
-    /// @dev Calculates a FillResults total for selling takerAssetFillAmount over all orders. 
-    ///      Including the fees required to be paid. 
-    /// @param orders An array of Order struct containing order specifications.
-    /// @param takerAssetFillAmount A number representing the amount of this order to fill.
-    /// @return totalFillResults Amounts filled and fees paid by maker and taker.
-    function calculateMarketSellResults(
-        LibOrder.Order[] memory orders,
-        uint256 takerAssetFillAmount
-    )
-        public
-        view
-        returns (FillResults memory totalFillResults)
-    {
-        for (uint256 i = 0; i < orders.length; i++) {
-            uint256 remainingTakerAssetFillAmount = safeSub(takerAssetFillAmount, totalFillResults.takerAssetFilledAmount);
-            FillResults memory singleFillResult = calculateFillResults(orders[i], remainingTakerAssetFillAmount);
-            addFillResults(totalFillResults, singleFillResult);
-            if (totalFillResults.takerAssetFilledAmount == takerAssetFillAmount) {
-                break;
-            }
-        }
-        return totalFillResults;
-    }
-
-    /// @dev Calculates fill results for buyFeeTokens. This handles fees on buying ZRX
-    ///      so the end result is the expected amount of ZRX (not less after fees).
-    /// @param orders An array of Order struct containing order specifications.
-    /// @param zrxFillAmount A number representing the amount zrx to buy
-    /// @return totalFillResults Expected fill result amounts from buying fees
-    function calculateMarketBuyZrxResults(
-        LibOrder.Order[] memory orders,
-        uint256 zrxFillAmount
-    )
-        public
-        view
-        returns (FillResults memory totalFillResults)
-    {
-        for (uint256 i = 0; i < orders.length; i++) {
-            uint256 remainingZrxFillAmount = safeSub(zrxFillAmount, totalFillResults.makerAssetFilledAmount);
-            // Convert the remaining amount of makerToken to buy into remaining amount
-            // of takerToken to sell, assuming entire amount can be sold in the current order
-            uint256 remainingWethSellAmount = getPartialAmount(
-                orders[i].takerAssetAmount,
-                safeSub(orders[i].makerAssetAmount, orders[i].takerFee), // our exchange rate after fees 
-                remainingZrxFillAmount
-            );
-            FillResults memory singleFillResult = calculateFillResults(orders[i], safeAdd(remainingWethSellAmount, 1));
-
-            singleFillResult.makerAssetFilledAmount = safeSub(singleFillResult.makerAssetFilledAmount, singleFillResult.takerFeePaid);
-            addFillResults(totalFillResults, singleFillResult);
-            // As we compensate for the rounding issue above have slightly more ZRX than the requested zrxFillAmount
-            if (totalFillResults.makerAssetFilledAmount >= zrxFillAmount) {
-                break;
-            }
-        }
-        return totalFillResults;
-    }
-
-    /// @dev Simulates the 0x Exchange fillOrder validation and calculations, without performing any state changes.
-    /// @param order An Order struct containing order specifications.
-    /// @param takerAssetFillAmount A number representing the amount of this order to fill.
-    /// @return fillResults Amounts filled and fees paid by maker and taker.
-    function calculateFillResults(
-        LibOrder.Order memory order,
-        uint256 takerAssetFillAmount
-    )
-        internal
-        view
-        returns (FillResults memory fillResults)
-    {
-        LibOrder.OrderInfo memory orderInfo = EXCHANGE.getOrderInfo(order);
-        if (orderInfo.orderStatus != uint8(LibOrder.OrderStatus.FILLABLE)) {
-            return fillResults;
-        }
-        uint256 remainingTakerAssetAmount = safeSub(order.takerAssetAmount, orderInfo.orderTakerAssetFilledAmount);
-        uint256 takerAssetFilledAmount = min256(takerAssetFillAmount, remainingTakerAssetAmount);
-
-        fillResults.takerAssetFilledAmount = takerAssetFilledAmount;
-        fillResults.makerAssetFilledAmount = getPartialAmount(
-            takerAssetFilledAmount,
-            order.takerAssetAmount,
-            order.makerAssetAmount
-        );
-        fillResults.makerFeePaid = getPartialAmount(
-            takerAssetFilledAmount,
-            order.takerAssetAmount,
-            order.makerFee
-        );
-        fillResults.takerFeePaid = getPartialAmount(
-            takerAssetFilledAmount,
-            order.takerAssetAmount,
-            order.takerFee
-        );
-        return fillResults;
-    }
-}
diff --git a/packages/contracts/src/2.0.0/forwarder/MixinFees.sol b/packages/contracts/src/2.0.0/forwarder/MixinFees.sol
deleted file mode 100644
index 8ea00a1d5..000000000
--- a/packages/contracts/src/2.0.0/forwarder/MixinFees.sol
+++ /dev/null
@@ -1,126 +0,0 @@
-/*
-
-  Copyright 2018 ZeroEx Intl.
-
-  Licensed under the Apache License, Version 2.0 (the "License");
-  you may not use this file except in compliance with the License.
-  You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-  Unless required by applicable law or agreed to in writing, software
-  distributed under the License is distributed on an "AS IS" BASIS,
-  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-  See the License for the specific language governing permissions and
-  limitations under the License.
-
-*/
-
-pragma solidity 0.4.24;
-
-import "../protocol/Exchange/libs/LibMath.sol";
-import "./mixins/MConstants.sol";
-import "./mixins/MFees.sol";
-
-
-contract MixinFees is
-    LibMath,
-    MConstants,
-    MFees
-{
-
-    uint16 constant public PERCENTAGE_DENOMINATOR = 10000; // 9800 == 98%, 10000 == 100%
-    uint16 constant public MAX_FEE = 1000; // 10%
-    uint16 constant public ALLOWABLE_EXCHANGE_PERCENTAGE = 9500; // 95%
-
-    /// @dev Default payabale function, this allows us to withdraw WETH
-    function ()
-        public
-        payable
-    {
-        require(
-            msg.sender == address(ETHER_TOKEN),
-            "DEFAULT_FUNCTION_WETH_CONTRACT_ONLY"
-        );
-    }
-
-    /// @dev Pays the feeRecipient feeProportion of the total takerEthAmount, denominated in ETH
-    /// @param takerEthAmount The total amount that was transacted in WETH, fees are calculated from this value.
-    /// @param feeProportion The proportion of fees
-    /// @param feeRecipient The recipient of the fees
-    /// @return ethFeeAmount Amount of ETH paid to feeRecipient as fee.
-    function payEthFee(
-        uint256 takerEthAmount,
-        uint16 feeProportion,
-        address feeRecipient
-    )
-        internal
-        returns (uint256 ethFeeAmount)
-    {
-        if (feeProportion > 0 && feeRecipient != address(0)) {
-            require(
-                feeProportion <= MAX_FEE,
-                "FEE_PROPORTION_TOO_LARGE"
-            );
-            // 1.5% is 150, allowing for 2 decimal precision, i.e 0.05% is 5
-            ethFeeAmount = getPartialAmount(
-                feeProportion,
-                PERCENTAGE_DENOMINATOR,
-                takerEthAmount
-            );
-            feeRecipient.transfer(ethFeeAmount);
-        }
-        return ethFeeAmount;
-    }
-
-    /// @dev Withdraws the remaining WETH, deduct and pay fees from this amount based on the takerTokenAmount to the feeRecipient.
-    ///      If a user overpaid ETH initially, the fees are calculated from the amount traded and deducted from withdrawAmount.
-    ///      Any remaining ETH is sent back to the user.
-    /// @param ethWithdrawAmount The amount to withdraw from the WETH contract.
-    /// @param wethAmountSold The total amount that was transacted in WETH, fees are calculated from this value.
-    /// @param feeProportion The proportion of fees
-    /// @param feeRecipient The recipient of the fees
-    function withdrawPayAndDeductEthFee(
-        uint256 ethWithdrawAmount,
-        uint256 wethAmountSold,
-        uint16 feeProportion,
-        address feeRecipient
-    )
-        internal
-    {
-        // Return all of the excess WETH if any after deducting fees on the amount
-        if (ethWithdrawAmount > 0) {
-            ETHER_TOKEN.withdraw(ethWithdrawAmount);
-            // Fees proportional to the amount traded
-            uint256 ethFeeAmount = payEthFee(
-                wethAmountSold,
-                feeProportion,
-                feeRecipient
-            );
-            uint256 unspentEthAmount = safeSub(ethWithdrawAmount, ethFeeAmount);
-            if (unspentEthAmount > 0) {
-                msg.sender.transfer(unspentEthAmount);
-            }
-        }
-    }
-
-    /// @dev Checks whether the amount of tokens sold against the amount of tokens requested
-    ///      is within a certain threshold. This ensures the caller gets a fair deal when
-    ///      performing any token fee abstraction. Threshold is 95%. If fee abstraction costs more than
-    ///      5% of the total transaction, we return false.
-    /// @param requestedSellAmount The amount the user requested, or sent in to a payable function
-    /// @param tokenAmountSold The amount of the token that was sold after fee abstraction
-    /// @return bool of whether this is within an acceptable threshold
-    function isAcceptableThreshold(uint256 requestedSellAmount, uint256 tokenAmountSold)
-        internal
-        pure
-        returns (bool)
-    {
-        uint256 acceptableSellAmount = getPartialAmount(
-            ALLOWABLE_EXCHANGE_PERCENTAGE,
-            PERCENTAGE_DENOMINATOR,
-            requestedSellAmount
-        );
-        return tokenAmountSold >= acceptableSellAmount;
-    }
-}
diff --git a/packages/contracts/src/2.0.0/forwarder/MixinForwarderCore.sol b/packages/contracts/src/2.0.0/forwarder/MixinForwarderCore.sol
index cb0ed5422..1164ae919 100644
--- a/packages/contracts/src/2.0.0/forwarder/MixinForwarderCore.sol
+++ b/packages/contracts/src/2.0.0/forwarder/MixinForwarderCore.sol
@@ -19,30 +19,30 @@
 pragma solidity 0.4.24;
 pragma experimental ABIEncoderV2;
 
-import "../utils/LibBytes/LibBytes.sol";
-import "./mixins/MFees.sol";
-import "./mixins/MMarketBuyZrx.sol";
-import "./mixins/MExpectedResults.sol";
-import "./mixins/MTransfer.sol";
-import "./mixins/MConstants.sol";
+import "./libs/LibConstants.sol";
+import "./mixins/MWeth.sol";
+import "./mixins/MAssets.sol";
+import "./mixins/MExchangeWrapper.sol";
 import "./mixins/MForwarderCore.sol";
+import "../utils/LibBytes/LibBytes.sol";
 import "../protocol/Exchange/libs/LibOrder.sol";
 import "../protocol/Exchange/libs/LibFillResults.sol";
+import "../protocol/Exchange/libs/LibMath.sol";
 
 
 contract MixinForwarderCore is
     LibFillResults,
-    MConstants,
-    MExpectedResults,
-    MFees,
-    MMarketBuyZrx,
-    MTransfer,
+    LibMath,
+    LibConstants,
+    MWeth,
+    MAssets,
+    MExchangeWrapper,
     MForwarderCore
 {
-    bytes4 constant internal ERC20_DATA_ID = bytes4(keccak256("ERC20Token(address)"));
-    bytes4 constant internal ERC721_DATA_ID = bytes4(keccak256("ERC721Token(address,uint256)"));
-    uint256 constant internal MAX_UINT = 2**256 - 1;
 
+    using LibBytes for bytes;
+
+    /// @dev Constructor approves ERC20 proxy to transfer ZRX and WETH on this contract's behalf.
     constructor ()
         public
     {
@@ -53,379 +53,202 @@ contract MixinForwarderCore is
         }
     }
 
-    /// @dev Market sells ETH for ERC20 tokens, performing fee abstraction if required. This does not support ERC721 tokens. This function is payable
-    ///      and will convert all incoming ETH into WETH and perform the trade on behalf of the caller.
-    ///      This function allows for a deduction of a proportion of incoming ETH sent to the feeRecipient.
-    ///      The caller is sent all tokens from the operation.
-    ///      If the purchased token amount does not meet an acceptable threshold then this function reverts.
-    /// @param orders An array of Order struct containing order specifications.
-    /// @param signatures An array of Proof that order has been created by maker.
-    /// @param feeOrders An array of Order struct containing order specifications for fees.
-    /// @param feeSignatures An array of Proof that order has been created by maker for the fee orders.
-    /// @param feeProportion A proportion deducted off the incoming ETH and sent to feeRecipient. The maximum value for this
-    ///        is 1000, aka 10%. Supports up to 2 decimal places. I.e 0.59% is 59.
-    /// @param feeRecipient An address of the fee recipient whom receives feeProportion of ETH.
-    /// @return FillResults amounts filled and fees paid by maker and taker.
-    function marketSellEthForERC20(
+    /// @dev Purchases as much of orders' makerAssets as possible by selling up to 95% of transaction's ETH value.
+    ///      Any ZRX required to pay fees for primary orders will automatically be purchased by this contract.
+    ///      5% of ETH value is reserved for paying fees to order feeRecipients (in ZRX) and forwarding contract feeRecipient (in ETH).
+    ///      Any ETH not spent will be refunded to sender.
+    /// @param orders Array of order specifications used containing desired makerAsset and WETH as takerAsset. 
+    /// @param signatures Proofs that orders have been created by makers.
+    /// @param feeOrders Array of order specifications containing ZRX as makerAsset and WETH as takerAsset. Used to purchase ZRX for primary order fees.
+    /// @param feeSignatures Proofs that feeOrders have been created by makers.
+    /// @param feePercentage Percentage of WETH sold that will payed as fee to forwarding contract feeRecipient.
+    /// @param feeRecipient Address that will receive ETH when orders are filled.
+    /// @return Amounts filled and fees paid by maker and taker for both sets of orders.
+    function marketSellOrdersWithEth(
         LibOrder.Order[] memory orders,
         bytes[] memory signatures,
         LibOrder.Order[] memory feeOrders,
         bytes[] memory feeSignatures,
-        uint16  feeProportion,
+        uint256  feePercentage,
         address feeRecipient
     )
         public
         payable
-        returns (FillResults memory totalFillResults)
+        returns (
+            FillResults memory orderFillResults,
+            FillResults memory feeOrderFillResults
+        )
     {
-        uint256 takerEthAmount = msg.value;
-        require(
-            takerEthAmount > 0,
-            "VALUE_GREATER_THAN_ZERO"
-        );
-        // Deduct the fee from the total amount of ETH sent in
-        uint256 ethFeeAmount = payEthFee(
-            takerEthAmount,
-            feeProportion,
-            feeRecipient
-        );
-        uint256 wethSellAmount = safeSub(takerEthAmount, ethFeeAmount);
-
-        // Deposit the remaining to be used for trading
-        ETHER_TOKEN.deposit.value(wethSellAmount)();
-        // Populate the known assetData, as it is always WETH the caller can provide null bytes to save gas
-        // marketSellOrders fills the remaining
-        address makerTokenAddress = LibBytes.readAddress(orders[0].makerAssetData, 16);
-        orders[0].takerAssetData = WETH_ASSET_DATA;
-        if (makerTokenAddress == address(ZRX_TOKEN)) {
-            // If this is ZRX then we market sell from the orders, rather than a 2 step of buying ZRX fees from feeOrders
-            // then buying ZRX from orders
-            totalFillResults = marketSellEthForZRXInternal(
+        // Convert ETH to WETH.
+        convertEthToWeth();
+
+        uint256 wethSellAmount;
+        uint256 zrxBuyAmount;
+        uint256 makerAssetAmountPurchased;
+        if (orders[0].makerAssetData.equals(ZRX_ASSET_DATA)) {
+            // Calculate amount of WETH that won't be spent on ETH fees.
+            wethSellAmount = getPartialAmount(
+                PERCENTAGE_DENOMINATOR,
+                safeAdd(PERCENTAGE_DENOMINATOR, feePercentage),
+                msg.value
+            );
+            // Market sell available WETH.
+            // ZRX fees are paid with this contract's balance.
+            orderFillResults = marketSellWeth(
                 orders,
-                signatures,
-                wethSellAmount
+                wethSellAmount,
+                signatures
             );
+            // The fee amount must be deducted from the amount transfered back to sender.
+            makerAssetAmountPurchased = safeSub(orderFillResults.makerAssetFilledAmount, orderFillResults.takerFeePaid);
         } else {
-            totalFillResults = marketSellEthForERC20Internal(
+            // 5% of WETH is reserved for filling feeOrders and paying feeRecipient.
+            wethSellAmount = getPartialAmount(
+                MAX_WETH_FILL_PERCENTAGE,
+                PERCENTAGE_DENOMINATOR,
+                msg.value
+            );
+            // Market sell 95% of WETH.
+            // ZRX fees are payed with this contract's balance.
+            orderFillResults = marketSellWeth(
                 orders,
-                signatures,
+                wethSellAmount,
+                signatures
+            );
+            // Buy back all ZRX spent on fees.
+            zrxBuyAmount = orderFillResults.takerFeePaid;
+            feeOrderFillResults = marketBuyZrxWithWeth(
                 feeOrders,
-                feeSignatures,
-                wethSellAmount
+                zrxBuyAmount,
+                feeSignatures
             );
+            makerAssetAmountPurchased = orderFillResults.makerAssetFilledAmount;
         }
-        // Prevent accidental WETH owned by this contract and it being spent
-        require(
-            takerEthAmount >= totalFillResults.takerAssetFilledAmount,
-            "INVALID_MSG_VALUE"
-        );
-        // Ensure no WETH is left in this contract
-        require(
-            wethSellAmount == totalFillResults.takerAssetFilledAmount,
-            "UNACCEPTABLE_THRESHOLD"
+
+        // Ensure that all ZRX fees have been repurchased and no extra WETH owned by this contract has been sold.
+        assertValidFillResults(
+            orderFillResults,
+            feeOrderFillResults,
+            zrxBuyAmount
         );
-        // Transfer all tokens to msg.sender
-        transferERC20Token(
-            makerTokenAddress,
-            msg.sender,
-            totalFillResults.makerAssetFilledAmount
+
+        // Transfer feePercentage of total ETH spent on primary orders to feeRecipient.
+        // Refund remaining ETH to msg.sender.
+        transferEthFeeAndRefund(
+            orderFillResults.takerAssetFilledAmount,
+            feeOrderFillResults.takerAssetFilledAmount,
+            feePercentage,
+            feeRecipient
         );
-        return totalFillResults;
+
+        // Transfer purchased assets to msg.sender.
+        transferPurchasedAssetToSender(orders[0].makerAssetData, makerAssetAmountPurchased);
     }
 
-    /// @dev Buys the exact amount of assets (ERC20 and ERC721), performing fee abstraction if required.
-    ///      All order assets must be of the same type. Deducts a proportional fee to fee recipient.
-    ///      This function is payable and will convert all incoming ETH into WETH and perform the trade on behalf of the caller.
-    ///      The caller is sent all assets from the fill of orders. This function will revert unless the requested amount of assets are purchased.
-    ///      Any excess ETH sent will be returned to the caller
-    /// @param orders An array of Order struct containing order specifications.
-    /// @param signatures An array of Proof that order has been created by maker.
-    /// @param feeOrders An array of Order struct containing order specifications for fees.
-    /// @param makerTokenFillAmount The amount of maker asset to buy.
-    /// @param feeSignatures An array of Proof that order has been created by maker for the fee orders.
-    /// @param feeProportion A proportion deducted off the ETH spent and sent to feeRecipient. The maximum value for this
-    ///        is 1000, aka 10%. Supports up to 2 decimal places. I.e 0.59% is 59.
-    /// @param feeRecipient An address of the fee recipient whom receives feeProportion of ETH.
-    /// @return FillResults amounts filled and fees paid by maker and taker.
-    function marketBuyTokensWithEth(
+    /// @dev Attempt to purchase makerAssetFillAmount of makerAsset by selling ETH provided with transaction.
+    ///      Any ZRX required to pay fees for primary orders will automatically be purchased by this contract.
+    ///      Any ETH not spent will be refunded to sender.
+    /// @param orders Array of order specifications used containing desired makerAsset and WETH as takerAsset. 
+    /// @param makerAssetFillAmount Desired amount of makerAsset to purchase.
+    /// @param signatures Proofs that orders have been created by makers.
+    /// @param feeOrders Array of order specifications containing ZRX as makerAsset and WETH as takerAsset. Used to purchase ZRX for primary order fees.
+    /// @param feeSignatures Proofs that feeOrders have been created by makers.
+    /// @param feePercentage Percentage of WETH sold that will payed as fee to forwarding contract feeRecipient.
+    /// @param feeRecipient Address that will receive ETH when orders are filled.
+    /// @return Amounts filled and fees paid by maker and taker for both sets of orders.
+    function marketBuyOrdersWithEth(
         LibOrder.Order[] memory orders,
+        uint256 makerAssetFillAmount,
         bytes[] memory signatures,
         LibOrder.Order[] memory feeOrders,
         bytes[] memory feeSignatures,
-        uint256 makerTokenFillAmount,
-        uint16  feeProportion,
+        uint256  feePercentage,
         address feeRecipient
     )
         public
         payable
-        returns (FillResults memory totalFillResults)
+        returns (
+            FillResults memory orderFillResults,
+            FillResults memory feeOrderFillResults
+        )
     {
-        uint256 takerEthAmount = msg.value;
-        require(
-            takerEthAmount > 0,
-            "VALUE_GREATER_THAN_ZERO"
-        );
-        require(
-            makerTokenFillAmount > 0,
-            "VALUE_GREATER_THAN_ZERO"
-        );
-        bytes4 assetDataId = LibBytes.readBytes4(orders[0].makerAssetData, 0);
-        require(
-            assetDataId == ERC20_DATA_ID || assetDataId == ERC721_DATA_ID,
-            "UNSUPPORTED_TOKEN_PROXY"
-        );
-
-        ETHER_TOKEN.deposit.value(takerEthAmount)();
-        if (assetDataId == ERC20_DATA_ID) {
-            totalFillResults = marketBuyERC20TokensInternal(
+        // Convert ETH to WETH.
+        convertEthToWeth();
+
+        uint256 zrxBuyAmount;
+        uint256 makerAssetAmountPurchased;
+        if (orders[0].makerAssetData.equals(ZRX_ASSET_DATA)) {
+            // If the makerAsset is ZRX, it is not necessary to pay fees out of this
+            // contracts's ZRX balance because fees are factored into the price of the order.
+            orderFillResults = marketBuyZrxWithWeth(
                 orders,
-                signatures,
-                feeOrders,
-                feeSignatures,
-                makerTokenFillAmount
+                makerAssetFillAmount,
+                signatures
             );
-        } else if (assetDataId == ERC721_DATA_ID) {
-            totalFillResults = batchBuyERC721TokensInternal(
+            // The fee amount must be deducted from the amount transfered back to sender.
+            makerAssetAmountPurchased = safeSub(orderFillResults.makerAssetFilledAmount, orderFillResults.takerFeePaid);
+        } else {
+            // Attemp to purchase desired amount of makerAsset.
+            // ZRX fees are payed with this contract's balance.
+            orderFillResults = marketBuyWithWeth(
                 orders,
-                signatures,
+                makerAssetFillAmount,
+                signatures
+            );
+            // Buy back all ZRX spent on fees.
+            zrxBuyAmount = orderFillResults.takerFeePaid;
+            feeOrderFillResults = marketBuyZrxWithWeth(
                 feeOrders,
+                zrxBuyAmount,
                 feeSignatures
             );
+            makerAssetAmountPurchased = orderFillResults.makerAssetFilledAmount;
         }
-        // Prevent accidental WETH owned by this contract and it being spent
-        require(
-            takerEthAmount >= totalFillResults.takerAssetFilledAmount,
-            "INVALID_MSG_VALUE"
+
+        // Ensure that all ZRX fees have been repurchased and no extra WETH owned by this contract has been sold.
+        assertValidFillResults(
+            orderFillResults,
+            feeOrderFillResults,
+            zrxBuyAmount
         );
-        withdrawPayAndDeductEthFee(
-            safeSub(takerEthAmount, totalFillResults.takerAssetFilledAmount),
-            totalFillResults.takerAssetFilledAmount,
-            feeProportion,
+
+        // Transfer feePercentage of total ETH spent on primary orders to feeRecipient.
+        // Refund remaining ETH to msg.sender.
+        transferEthFeeAndRefund(
+            orderFillResults.takerAssetFilledAmount,
+            feeOrderFillResults.takerAssetFilledAmount,
+            feePercentage,
             feeRecipient
         );
-        return totalFillResults;
-    }
 
-    /// @dev Market sells WETH for ERC20 tokens.
-    /// @param orders An array of Order struct containing order specifications.
-    /// @param signatures An array of Proof that order has been created by maker.
-    /// @param feeOrders An array of Order struct containing order specifications for fees.
-    /// @param feeSignatures An array of Proof that order has been created by maker for the fee orders.
-    /// @param wethSellAmount The amount of WETH to sell.
-    /// @return FillResults amounts filled and fees paid by maker and taker.
-    function marketSellEthForERC20Internal(
-        LibOrder.Order[] memory orders,
-        bytes[] memory signatures,
-        LibOrder.Order[] memory feeOrders,
-        bytes[] memory feeSignatures,
-        uint256 wethSellAmount
-    )
-        internal
-        returns (FillResults memory totalFillResults)
-    {
-        uint256 remainingWethSellAmount = wethSellAmount;
-        FillResults memory calculatedMarketSellResults = calculateMarketSellResults(orders, wethSellAmount);
-        if (calculatedMarketSellResults.takerFeePaid > 0) {
-            // Fees are required for these orders. Buy enough ZRX to cover the future market buy
-            FillResults memory feeTokensResults = marketBuyZrxInternal(
-                feeOrders,
-                feeSignatures,
-                calculatedMarketSellResults.takerFeePaid
-            );
-            // Ensure the token abstraction was fair if fees were proportionally too high, we fail
-            require(
-                isAcceptableThreshold(
-                    wethSellAmount,
-                    safeSub(wethSellAmount, feeTokensResults.takerAssetFilledAmount)
-                ),
-                "UNACCEPTABLE_THRESHOLD"
-            );
-            remainingWethSellAmount = safeSub(remainingWethSellAmount, feeTokensResults.takerAssetFilledAmount);
-            totalFillResults.takerFeePaid = feeTokensResults.takerFeePaid;
-            totalFillResults.takerAssetFilledAmount = feeTokensResults.takerAssetFilledAmount;
-        }
-        // Make our market sell to buy the requested tokens with the remaining balance
-        FillResults memory requestedTokensResults = EXCHANGE.marketSellOrders(
-            orders,
-            remainingWethSellAmount,
-            signatures
-        );
-        // Update our return FillResult with the market sell
-        addFillResults(totalFillResults, requestedTokensResults);
-        return totalFillResults;
+        // Transfer purchased assets to msg.sender.
+        transferPurchasedAssetToSender(orders[0].makerAssetData, makerAssetAmountPurchased);
     }
 
-    /// @dev Market sells WETH for ZRX tokens.
-    /// @param orders An array of Order struct containing order specifications.
-    /// @param signatures An array of Proof that order has been created by maker.
-    /// @param wethSellAmount The amount of WETH to sell.
-    /// @return FillResults amounts filled and fees paid by maker and taker.
-    function marketSellEthForZRXInternal(
-        LibOrder.Order[] memory orders,
-        bytes[] memory signatures,
-        uint256 wethSellAmount
+    /// @dev Ensures that all ZRX fees have been repurchased and no extra WETH owned by this contract has been sold.
+    /// @param orderFillResults Amounts filled and fees paid for primary orders.
+    /// @param feeOrderFillResults Amounts filled and fees paid for fee orders.
+    /// @param zrxBuyAmount The amount of ZRX that needed to be repurchased after filling primary orders.
+    function assertValidFillResults(
+        FillResults memory orderFillResults,
+        FillResults memory feeOrderFillResults,
+        uint256 zrxBuyAmount
     )
         internal
-        returns (FillResults memory totalFillResults)
+        view
     {
-        // Make our market sell to buy the requested tokens with the remaining balance
-        totalFillResults = EXCHANGE.marketSellOrders(
-            orders,
-            wethSellAmount,
-            signatures
-        );
-        // Exchange does not special case ZRX in the makerAssetFilledAmount, if fees were deducted then using this amount
-        // for future transfers is invalid.
-        uint256 zrxAmountBought = safeSub(totalFillResults.makerAssetFilledAmount, totalFillResults.takerFeePaid);
+        // Ensure that all ZRX spent while filling primary orders has been repurchased.
+        uint256 zrxPurchased = safeSub(feeOrderFillResults.makerAssetFilledAmount, feeOrderFillResults.takerFeePaid);
         require(
-            isAcceptableThreshold(totalFillResults.makerAssetFilledAmount, zrxAmountBought),
-            "UNACCEPTABLE_THRESHOLD"
+            zrxPurchased >= zrxBuyAmount,
+            "COMPLETE_FILL_FAILED"
         );
-        totalFillResults.makerAssetFilledAmount = zrxAmountBought;
-        return totalFillResults;
-    }
 
-    /// @dev Buys an exact amount of an ERC20 token using WETH.
-    /// @param orders Orders to fill. The maker asset is the ERC20 token to buy. The taker asset is WETH.
-    /// @param signatures Proof that the orders were created by their respective makers.
-    /// @param feeOrders to fill. The maker asset is ZRX and the taker asset is WETH.
-    /// @param feeSignatures Proof that the feeOrders were created by their respective makers.
-    /// @param makerTokenFillAmount Amount of the ERC20 token to buy.
-    /// @return totalFillResults Aggregated fill results of buying the ERC20 and ZRX tokens.
-    function marketBuyERC20TokensInternal(
-        LibOrder.Order[] memory orders,
-        bytes[] memory signatures,
-        LibOrder.Order[] memory feeOrders,
-        bytes[] memory feeSignatures,
-        uint256 makerTokenFillAmount
-    )
-        internal
-        returns (LibFillResults.FillResults memory totalFillResults)
-    {
-        // We read the maker token address to check if it is ZRX and later use it for transfer
-        address makerTokenAddress = LibBytes.readAddress(orders[0].makerAssetData, 16);
-        // We assume that asset being bought by taker is the same for each order.
-        // Rather than passing this in as calldata, we copy the makerAssetData from the first order onto all later orders.
-        orders[0].takerAssetData = WETH_ASSET_DATA;
-        // We can short cut here for effeciency and use buyFeeTokensInternal if maker asset token is ZRX
-        // this buys us exactly that amount taking into account the fees. This saves gas and calculates the rate correctly
-        FillResults memory marketBuyResults;
-        if (makerTokenAddress == address(ZRX_TOKEN)) {
-            marketBuyResults = marketBuyZrxInternal(
-                orders,
-                signatures,
-                makerTokenFillAmount
-            );
-            // When buying ZRX we round up which can result in a small margin excess
-            require(
-                marketBuyResults.makerAssetFilledAmount >= makerTokenFillAmount,
-                "UNACCEPTABLE_THRESHOLD"
-            );
-            addFillResults(totalFillResults, marketBuyResults);
-            require(
-                isAcceptableThreshold(
-                    safeAdd(totalFillResults.makerAssetFilledAmount, totalFillResults.takerFeePaid), // Total ZRX
-                    totalFillResults.makerAssetFilledAmount // amount going to msg.sender
-                ),
-                "UNACCEPTABLE_THRESHOLD"
-            );
-        } else {
-            FillResults memory calculatedMarketBuyResults = calculateMarketBuyResults(orders, makerTokenFillAmount);
-            if (calculatedMarketBuyResults.takerFeePaid > 0) {
-                // Fees are required for these orders. Buy enough ZRX to cover the future market buy
-                FillResults memory zrxMarketBuyResults = marketBuyZrxInternal(
-                    feeOrders,
-                    feeSignatures,
-                    calculatedMarketBuyResults.takerFeePaid
-                );
-                totalFillResults.takerAssetFilledAmount = zrxMarketBuyResults.takerAssetFilledAmount;
-                totalFillResults.takerFeePaid = zrxMarketBuyResults.takerFeePaid;
-            }
-            // Make our market buy of the requested tokens with the remaining balance
-            marketBuyResults = EXCHANGE.marketBuyOrders(
-                orders,
-                makerTokenFillAmount,
-                signatures
-            );
-            require(
-                marketBuyResults.makerAssetFilledAmount == makerTokenFillAmount,
-                "UNACCEPTABLE_THRESHOLD"
-            );
-            addFillResults(totalFillResults, marketBuyResults);
-            require(
-                isAcceptableThreshold(
-                    totalFillResults.takerAssetFilledAmount,
-                    marketBuyResults.takerAssetFilledAmount
-                ),
-                "UNACCEPTABLE_THRESHOLD"
-            );
-        }
-        // Transfer all purchased tokens to msg.sender
-        transferERC20Token(
-            makerTokenAddress,
-            msg.sender,
-            marketBuyResults.makerAssetFilledAmount
-        );
-        return totalFillResults;
-    }
-
-    /// @dev Buys an all of the ERC721 tokens in the orders.
-    /// @param orders Orders to fill. The maker asset is the ERC721 token to buy. The taker asset is WETH.
-    /// @param signatures Proof that the orders were created by their respective makers.
-    /// @param feeOrders to fill. The maker asset is ZRX and the taker asset is WETH.
-    /// @param feeSignatures Proof that the feeOrders were created by their respective makers.
-    /// @return totalFillResults Aggregated fill results of buying the ERC721 tokens and ZRX tokens.
-    function batchBuyERC721TokensInternal(
-        LibOrder.Order[] memory orders,
-        bytes[] memory signatures,
-        LibOrder.Order[] memory feeOrders,
-        bytes[] memory feeSignatures
-    )
-        internal
-        returns (LibFillResults.FillResults memory totalFillResults)
-    {
-        uint256 totalZrxFeeAmount;
-        uint256 ordersLength = orders.length;
-        uint256[] memory takerAssetFillAmounts = new uint256[](ordersLength);
-        for (uint256 i = 0; i < ordersLength; i++) {
-            // Total up the fees
-            totalZrxFeeAmount = safeAdd(totalZrxFeeAmount, orders[i].takerFee);
-            // We assume that asset being bought by taker is the same for each order.
-            // Rather than passing this in as calldata, we set the takerAssetData as WETH asset data
-            orders[i].takerAssetData = WETH_ASSET_DATA;
-            // Populate takerAssetFillAmounts for later batchFill
-            takerAssetFillAmounts[i] = orders[i].takerAssetAmount;
-        }
-        if (totalZrxFeeAmount > 0) {
-            // Fees are required for these orders. Buy enough ZRX to cover the future fill
-            FillResults memory zrxMarketBuyResults = marketBuyZrxInternal(
-                feeOrders,
-                feeSignatures,
-                totalZrxFeeAmount
-            );
-            totalFillResults.takerFeePaid = zrxMarketBuyResults.takerFeePaid;
-            totalFillResults.takerAssetFilledAmount = zrxMarketBuyResults.takerAssetFilledAmount;
-        }
-        FillResults memory batchFillResults = EXCHANGE.batchFillOrKillOrders(
-            orders,
-            takerAssetFillAmounts,
-            signatures
-        );
-        addFillResults(totalFillResults, batchFillResults);
+        // Ensure that no extra WETH owned by this contract has been sold.
+        uint256 wethSold = safeAdd(orderFillResults.takerAssetFilledAmount, feeOrderFillResults.takerAssetFilledAmount);
         require(
-            isAcceptableThreshold(
-                totalFillResults.takerAssetFilledAmount,
-                batchFillResults.takerAssetFilledAmount
-            ),
-            "UNACCEPTABLE_THRESHOLD"
+            wethSold <= msg.value,
+            "OVERSOLD_WETH"
         );
-        // Transfer all of the tokens filled from the batchFill
-        for (i = 0; i < ordersLength; i++) {
-            transferERC721Token(
-                orders[i].makerAssetData,
-                msg.sender
-            );
-        }
-        return totalFillResults;
     }
 }
diff --git a/packages/contracts/src/2.0.0/forwarder/MixinMarketBuyZrx.sol b/packages/contracts/src/2.0.0/forwarder/MixinMarketBuyZrx.sol
deleted file mode 100644
index e272f8aad..000000000
--- a/packages/contracts/src/2.0.0/forwarder/MixinMarketBuyZrx.sol
+++ /dev/null
@@ -1,83 +0,0 @@
-/*
-
-  Copyright 2018 ZeroEx Intl.
-
-  Licensed under the Apache License, Version 2.0 (the "License");
-  you may not use this file except in compliance with the License.
-  You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-  Unless required by applicable law or agreed to in writing, software
-  distributed under the License is distributed on an "AS IS" BASIS,
-  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-  See the License for the specific language governing permissions and
-  limitations under the License.
-
-*/
-
-pragma solidity 0.4.24;
-pragma experimental ABIEncoderV2;
-
-import "../protocol/Exchange/libs/LibFillResults.sol";
-import "../protocol/Exchange/libs/LibOrder.sol";
-import "../protocol/Exchange/libs/LibMath.sol";
-import "./mixins/MConstants.sol";
-import "./mixins/MMarketBuyZrx.sol";
-
-
-contract MixinMarketBuyZrx is
-    LibMath,
-    LibFillResults,
-    MConstants,
-    MMarketBuyZrx
-{
-
-    /// @dev Buys zrxBuyAmount of ZRX fee tokens, taking into account the fees on buying fee tokens. This will guarantee
-    ///      At least zrxBuyAmount of ZRX fee tokens are purchased (sometimes slightly over due to rounding issues).
-    ///      It is possible that a request to buy 200 ZRX fee tokens will require purchasing 202 ZRX tokens
-    ///      As 2 ZRX is required to purchase the 200 ZRX fee tokens. This guarantees at least 200 ZRX for future purchases.
-    /// @param orders An array of Order struct containing order specifications for fees.
-    /// @param signatures An array of Proof that order has been created by maker for the fee orders.
-    /// @param zrxBuyAmount The number of requested ZRX fee tokens.
-    /// @return totalFillResults Amounts filled and fees paid by maker and taker. makerTokenAmount is the zrx amount deducted of fees
-    function marketBuyZrxInternal(
-        LibOrder.Order[] memory orders,
-        bytes[] memory signatures,
-        uint256 zrxBuyAmount
-    )
-        internal
-        returns (FillResults memory totalFillResults)
-    {
-        for (uint256 i = 0; i < orders.length; i++) {
-            // All of these are ZRX/WETH, we can drop the respective assetData from callData
-            orders[i].makerAssetData = ZRX_ASSET_DATA;
-            orders[i].takerAssetData = WETH_ASSET_DATA;
-            // Calculate the remaining amount of makerToken to buy
-            uint256 remainingZrxBuyAmount = safeSub(zrxBuyAmount, totalFillResults.makerAssetFilledAmount);
-            // Convert the remaining amount of makerToken to buy into remaining amount
-            // of takerToken to sell, assuming entire amount can be sold in the current order
-            uint256 remainingWethSellAmount = getPartialAmount(
-                orders[i].takerAssetAmount,
-                safeSub(orders[i].makerAssetAmount, orders[i].takerFee), // our exchange rate after fees 
-                remainingZrxBuyAmount
-            );
-            // Attempt to sell the remaining amount of takerToken
-            // Round up the amount to ensure we don't under buy by a fractional amount
-            FillResults memory singleFillResult = EXCHANGE.fillOrder(
-                orders[i],
-                safeAdd(remainingWethSellAmount, 1),
-                signatures[i]
-            );
-            // We didn't buy the full amount when buying ZRX as some were taken for fees
-            singleFillResult.makerAssetFilledAmount = safeSub(singleFillResult.makerAssetFilledAmount, singleFillResult.takerFeePaid);
-            // Update amounts filled and fees paid by maker and taker
-            addFillResults(totalFillResults, singleFillResult);
-            // Stop execution if the entire amount of makerToken has been bought
-            if (totalFillResults.makerAssetFilledAmount >= zrxBuyAmount) {
-                break;
-            }
-        }
-        return totalFillResults;
-    }
-}
diff --git a/packages/contracts/src/2.0.0/forwarder/MixinWeth.sol b/packages/contracts/src/2.0.0/forwarder/MixinWeth.sol
new file mode 100644
index 000000000..8ba236e7f
--- /dev/null
+++ b/packages/contracts/src/2.0.0/forwarder/MixinWeth.sol
@@ -0,0 +1,110 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity 0.4.24;
+
+import "../protocol/Exchange/libs/LibMath.sol";
+import "./libs/LibConstants.sol";
+import "./mixins/MWeth.sol";
+
+
+contract MixinWeth is
+    LibMath,
+    LibConstants,
+    MWeth
+{
+
+    /// @dev Default payabale function, this allows us to withdraw WETH
+    function ()
+        public
+        payable
+    {
+        require(
+            msg.sender == address(ETHER_TOKEN),
+            "DEFAULT_FUNCTION_WETH_CONTRACT_ONLY"
+        );
+    }
+
+    /// @dev Converts message call's ETH value into WETH.
+    function convertEthToWeth()
+        internal
+    {
+        require(
+            msg.value > 0,
+            "INVALID_MSG_VALUE"
+        );
+        ETHER_TOKEN.deposit.value(msg.value)();
+    }
+
+    /// @dev Transfers feePercentage of WETH spent on primary orders to feeRecipient.
+    ///      Refunds any excess ETH to msg.sender.
+    /// @param wethSoldExcludingFeeOrders Amount of WETH sold when filling primary orders.
+    /// @param wethSoldForZrx Amount of WETH sold when purchasing ZRX required for primary order fees.
+    /// @param feePercentage Percentage of WETH sold that will payed as fee to forwarding contract feeRecipient.
+    /// @param feeRecipient Address that will receive ETH when orders are filled.
+    function transferEthFeeAndRefund(
+        uint256 wethSoldExcludingFeeOrders,
+        uint256 wethSoldForZrx,
+        uint256 feePercentage,
+        address feeRecipient
+    )
+        internal
+    {
+        // Ensure feePercentage is less than 5%.
+        require(
+            feePercentage <= MAX_FEE_PERCENTAGE,
+            "FEE_PERCENTAGE_TOO_LARGE"
+        );
+
+        // Calculate amount of WETH that hasn't been sold.
+        uint256 wethRemaining = safeSub(
+            msg.value,
+            safeAdd(wethSoldExcludingFeeOrders, wethSoldForZrx)
+        );
+
+        // Calculate ETH fee to pay to feeRecipient.
+        uint256 ethFee = getPartialAmount(
+            feePercentage,
+            PERCENTAGE_DENOMINATOR,
+            wethSoldExcludingFeeOrders
+        );
+
+        // Ensure fee is less than amount of WETH remaining.
+        require(
+            ethFee <= wethRemaining,
+            "INSUFFICIENT_ETH_REMAINING"
+        );
+    
+        // Do nothing if no WETH remaining
+        if (wethRemaining > 0) {
+            // Convert remaining WETH to ETH
+            ETHER_TOKEN.withdraw(wethRemaining);
+
+            // Pay ETH to feeRecipient
+            if (ethFee > 0) {
+                feeRecipient.transfer(ethFee);
+            }
+
+            // Refund remaining ETH to msg.sender.
+            uint256 ethRefund = safeSub(wethRemaining, ethFee);
+            if (ethRefund > 0) {
+                msg.sender.transfer(ethRefund);
+            }
+        }
+    }
+}
diff --git a/packages/contracts/src/2.0.0/forwarder/mixins/MTransfer.sol b/packages/contracts/src/2.0.0/forwarder/interfaces/IAssets.sol
index 418a6288b..9b0d995eb 100644
--- a/packages/contracts/src/2.0.0/forwarder/mixins/MTransfer.sol
+++ b/packages/contracts/src/2.0.0/forwarder/interfaces/IAssets.sol
@@ -19,28 +19,16 @@
 pragma solidity 0.4.24;
 
 
-contract MTransfer {
-
-    function onERC721Received(address, uint256, bytes memory)
-        public
-        pure
-        returns(bytes4);
-
-    function onERC721Received(address, address, uint256, bytes memory)
-        public
-        pure
-        returns(bytes4);
-    
-    function transferERC20Token(
+contract IAssets {
+
+    /// @dev Withdraws ERC20 tokens from this contract. The contract requires a ZRX balance in order to 
+    ///      function optimally, and this function allows the ZRX to be withdrawn by owner. It may also be
+    ///      used to withdraw tokens that were accidentally sent to this contract.
+    /// @param token Address of ERC20 token to withdraw.
+    /// @param amount Amount of ERC20 token to withdraw.
+    function withdrawERC20(
         address token,
-        address to,
         uint256 amount
     )
-        internal;
-
-    function transferERC721Token(
-        bytes memory assetData,
-        address to
-    )
-        internal;
+        external;
 }
diff --git a/packages/contracts/src/2.0.0/forwarder/interfaces/IExpectedResults.sol b/packages/contracts/src/2.0.0/forwarder/interfaces/IExpectedResults.sol
deleted file mode 100644
index 89187b750..000000000
--- a/packages/contracts/src/2.0.0/forwarder/interfaces/IExpectedResults.sol
+++ /dev/null
@@ -1,66 +0,0 @@
-/*
-
-  Copyright 2018 ZeroEx Intl.
-
-  Licensed under the Apache License, Version 2.0 (the "License");
-  you may not use this file except in compliance with the License.
-  You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-  Unless required by applicable law or agreed to in writing, software
-  distributed under the License is distributed on an "AS IS" BASIS,
-  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-  See the License for the specific language governing permissions and
-  limitations under the License.
-
-*/
-
-pragma solidity 0.4.24;
-pragma experimental ABIEncoderV2;
-
-import "../../protocol/Exchange/libs/LibFillResults.sol";
-import "../../protocol/Exchange/libs/LibOrder.sol";
-
-
-contract IExpectedResults {
-
-    /// @dev Calculates a total FillResults for buying makerAssetFillAmount over all orders.
-    ///      Including the fees required to be paid. 
-    /// @param orders An array of Order struct containing order specifications.
-    /// @param makerAssetFillAmount A number representing the amount of this order to fill.
-    /// @return totalFillResults Amounts filled and fees paid by maker and taker.
-    function calculateMarketBuyResults(
-        LibOrder.Order[] memory orders,
-        uint256 makerAssetFillAmount
-    )
-        public
-        view
-        returns (LibFillResults.FillResults memory totalFillResults);
-
-    /// @dev Calculates a FillResults total for selling takerAssetFillAmount over all orders. 
-    ///      Including the fees required to be paid. 
-    /// @param orders An array of Order struct containing order specifications.
-    /// @param takerAssetFillAmount A number representing the amount of this order to fill.
-    /// @return totalFillResults Amounts filled and fees paid by maker and taker.
-    function calculateMarketSellResults(
-        LibOrder.Order[] memory orders,
-        uint256 takerAssetFillAmount
-    )
-        public
-        view
-        returns (LibFillResults.FillResults memory totalFillResults);
-
-    /// @dev Calculates fill results for buyFeeTokens. This handles fees on buying ZRX
-    ///      so the end result is the expected amount of ZRX (not less after fees).
-    /// @param orders An array of Order struct containing order specifications.
-    /// @param zrxFillAmount A number representing the amount zrx to buy
-    /// @return totalFillResults Expected fill result amounts from buying fees
-    function calculateMarketBuyZrxResults(
-        LibOrder.Order[] memory orders,
-        uint256 zrxFillAmount
-    )
-        public
-        view
-        returns (LibFillResults.FillResults memory totalFillResults);
-}
diff --git a/packages/contracts/src/2.0.0/forwarder/interfaces/IForwarder.sol b/packages/contracts/src/2.0.0/forwarder/interfaces/IForwarder.sol
index 745dd29a9..f5a26e2ba 100644
--- a/packages/contracts/src/2.0.0/forwarder/interfaces/IForwarder.sol
+++ b/packages/contracts/src/2.0.0/forwarder/interfaces/IForwarder.sol
@@ -20,11 +20,11 @@ pragma solidity 0.4.24;
 pragma experimental ABIEncoderV2;
 
 import "./IForwarderCore.sol";
-import "./IExpectedResults.sol";
+import "./IAssets.sol";
 
 
 // solhint-disable no-empty-blocks
 contract IForwarder is
     IForwarderCore,
-    IExpectedResults
+    IAssets
 {}
diff --git a/packages/contracts/src/2.0.0/forwarder/interfaces/IForwarderCore.sol b/packages/contracts/src/2.0.0/forwarder/interfaces/IForwarderCore.sol
index 7ac2a8af3..3ecbb133b 100644
--- a/packages/contracts/src/2.0.0/forwarder/interfaces/IForwarderCore.sol
+++ b/packages/contracts/src/2.0.0/forwarder/interfaces/IForwarderCore.sol
@@ -25,55 +25,56 @@ import "../../protocol/Exchange/libs/LibFillResults.sol";
 
 contract IForwarderCore {
 
-    /// @dev Market sells ETH for ERC20 tokens, performing fee abstraction if required. This does not support ERC721 tokens. This function is payable
-    ///      and will convert all incoming ETH into WETH and perform the trade on behalf of the caller.
-    ///      This function allows for a deduction of a proportion of incoming ETH sent to the feeRecipient.
-    ///      The caller is sent all tokens from the operation.
-    ///      If the purchased token amount does not meet an acceptable threshold then this function reverts.
-    /// @param orders An array of Order struct containing order specifications.
-    /// @param signatures An array of Proof that order has been created by maker.
-    /// @param feeOrders An array of Order struct containing order specifications for fees.
-    /// @param feeSignatures An array of Proof that order has been created by maker for the fee orders.
-    /// @param feeProportion A proportion deducted off the incoming ETH and sent to feeRecipient. The maximum value for this
-    ///        is 1000, aka 10%. Supports up to 2 decimal places. I.e 0.59% is 59.
-    /// @param feeRecipient An address of the fee recipient whom receives feeProportion of ETH.
-    /// @return FillResults amounts filled and fees paid by maker and taker.
-    function marketSellEthForERC20(
+    /// @dev Purchases as much of orders' makerAssets as possible by selling up to 95% of transaction's ETH value.
+    ///      Any ZRX required to pay fees for primary orders will automatically be purchased by this contract.
+    ///      5% of ETH value is reserved for paying fees to order feeRecipients (in ZRX) and forwarding contract feeRecipient (in ETH).
+    ///      Any ETH not spent will be refunded to sender.
+    /// @param orders Array of order specifications used containing desired makerAsset and WETH as takerAsset. 
+    /// @param signatures Proofs that orders have been created by makers.
+    /// @param feeOrders Array of order specifications containing ZRX as makerAsset and WETH as takerAsset. Used to purchase ZRX for primary order fees.
+    /// @param feeSignatures Proofs that feeOrders have been created by makers.
+    /// @param feePercentage Percentage of WETH sold that will payed as fee to forwarding contract feeRecipient.
+    /// @param feeRecipient Address that will receive ETH when orders are filled.
+    /// @return Amounts filled and fees paid by maker and taker for both sets of orders.
+    function marketSellOrdersWithEth(
         LibOrder.Order[] memory orders,
         bytes[] memory signatures,
         LibOrder.Order[] memory feeOrders,
         bytes[] memory feeSignatures,
-        uint16  feeProportion,
+        uint256  feePercentage,
         address feeRecipient
     )
         public
         payable
-        returns (LibFillResults.FillResults memory totalFillResults);
+        returns (
+            LibFillResults.FillResults memory orderFillResults,
+            LibFillResults.FillResults memory feeOrderFillResults
+        );
 
-    /// @dev Buys the exact amount of assets (ERC20 and ERC721), performing fee abstraction if required.
-    ///      All order assets must be of the same type. Deducts a proportional fee to fee recipient.
-    ///      This function is payable and will convert all incoming ETH into WETH and perform the trade on behalf of the caller.
-    ///      The caller is sent all assets from the fill of orders. This function will revert unless the requested amount of assets are purchased.
-    ///      Any excess ETH sent will be returned to the caller
-    /// @param orders An array of Order struct containing order specifications.
-    /// @param signatures An array of Proof that order has been created by maker.
-    /// @param feeOrders An array of Order struct containing order specifications for fees.
-    /// @param makerTokenFillAmount The amount of maker asset to buy.
-    /// @param feeSignatures An array of Proof that order has been created by maker for the fee orders.
-    /// @param feeProportion A proportion deducted off the ETH spent and sent to feeRecipient. The maximum value for this
-    ///        is 1000, aka 10%. Supports up to 2 decimal places. I.e 0.59% is 59.
-    /// @param feeRecipient An address of the fee recipient whom receives feeProportion of ETH.
-    /// @return FillResults amounts filled and fees paid by maker and taker.
-    function marketBuyTokensWithEth(
+    /// @dev Attempt to purchase makerAssetFillAmount of makerAsset by selling ETH provided with transaction.
+    ///      Any ZRX required to pay fees for primary orders will automatically be purchased by this contract.
+    ///      Any ETH not spent will be refunded to sender.
+    /// @param orders Array of order specifications used containing desired makerAsset and WETH as takerAsset. 
+    /// @param makerAssetFillAmount Desired amount of makerAsset to purchase.
+    /// @param signatures Proofs that orders have been created by makers.
+    /// @param feeOrders Array of order specifications containing ZRX as makerAsset and WETH as takerAsset. Used to purchase ZRX for primary order fees.
+    /// @param feeSignatures Proofs that feeOrders have been created by makers.
+    /// @param feePercentage Percentage of WETH sold that will payed as fee to forwarding contract feeRecipient.
+    /// @param feeRecipient Address that will receive ETH when orders are filled.
+    /// @return Amounts filled and fees paid by maker and taker for both sets of orders.
+    function marketBuyOrdersWithEth(
         LibOrder.Order[] memory orders,
+        uint256 makerAssetFillAmount,
         bytes[] memory signatures,
         LibOrder.Order[] memory feeOrders,
         bytes[] memory feeSignatures,
-        uint256 makerTokenFillAmount,
-        uint16  feeProportion,
+        uint256  feePercentage,
         address feeRecipient
     )
         public
         payable
-        returns (LibFillResults.FillResults memory totalFillResults);
+        returns (
+            LibFillResults.FillResults memory orderFillResults,
+            LibFillResults.FillResults memory feeOrderFillResults
+        );
 }
diff --git a/packages/contracts/src/2.0.0/forwarder/MixinConstants.sol b/packages/contracts/src/2.0.0/forwarder/libs/LibConstants.sol
index 2b064d579..c26d7902c 100644
--- a/packages/contracts/src/2.0.0/forwarder/MixinConstants.sol
+++ b/packages/contracts/src/2.0.0/forwarder/libs/LibConstants.sol
@@ -18,12 +18,27 @@
 
 pragma solidity 0.4.24;
 
-import "./mixins/MConstants.sol";
-
-
-contract MixinConstants is
-    MConstants
-{
+import "../../protocol/Exchange/interfaces/IExchange.sol";
+import "../../tokens/EtherToken/IEtherToken.sol";
+import "../../tokens/ERC20Token/IERC20Token.sol";
+
+
+contract LibConstants {
+
+    bytes4 constant internal ERC20_DATA_ID = bytes4(keccak256("ERC20Token(address)"));
+    bytes4 constant internal ERC721_DATA_ID = bytes4(keccak256("ERC721Token(address,uint256)"));
+    uint256 constant internal MAX_UINT = 2**256 - 1;
+    uint256 constant internal PERCENTAGE_DENOMINATOR = 10**18; 
+    uint256 constant internal MAX_FEE_PERCENTAGE = 5 * PERCENTAGE_DENOMINATOR / 100;         // 5%
+    uint256 constant internal MAX_WETH_FILL_PERCENTAGE = 95 * PERCENTAGE_DENOMINATOR / 100;  // 95%
+ 
+     // solhint-disable var-name-mixedcase
+    IExchange internal EXCHANGE;
+    IEtherToken internal ETHER_TOKEN;
+    IERC20Token internal ZRX_TOKEN;
+    bytes internal ZRX_ASSET_DATA;
+    bytes internal WETH_ASSET_DATA;
+    // solhint-enable var-name-mixedcase
 
     constructor (
         address _exchange,
diff --git a/packages/contracts/src/2.0.0/forwarder/libs/LibForwarderErrors.sol b/packages/contracts/src/2.0.0/forwarder/libs/LibForwarderErrors.sol
new file mode 100644
index 000000000..cdfb77a0b
--- /dev/null
+++ b/packages/contracts/src/2.0.0/forwarder/libs/LibForwarderErrors.sol
@@ -0,0 +1,34 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+// solhint-disable
+pragma solidity 0.4.24;
+
+
+/// This contract is intended to serve as a reference, but is not actually used for efficiency reasons.
+contract LibForwarderErrors {
+    string constant FEE_PERCENTAGE_TOO_LARGE = "FEE_PROPORTION_TOO_LARGE";                        // Provided fee percentage greater than 5%.
+    string constant INSUFFICIENT_ETH_REMAINING = "INSUFFICIENT_ETH_REMAINING";                    // Not enough ETH remaining to pay feeRecipient.
+    string constant OVERSOLD_WETH = "OVERSOLD_WETH";                                              // More WETH sold than provided with current message call.
+    string constant COMPLETE_FILL_FAILED = "COMPLETE_FILL_FAILED";                                // Desired purchase amount not completely filled (required for ZRX fees only).
+    string constant TRANSFER_FAILED = "TRANSFER_FAILED";                                          // Asset transfer failed.
+    string constant UNSUPPORTED_TOKEN_PROXY = "UNSUPPORTED_TOKEN_PROXY";                          // Proxy in assetData not supported.
+    string constant DEFAULT_FUNCTION_WETH_CONTRACT_ONLY = "DEFAULT_FUNCTION_WETH_CONTRACT_ONLY";  // Fallback function may only be used for WETH withdrawals.
+    string constant INVALID_MSG_VALUE = "INVALID_MSG_VALUE";                                      // msg.value must be greater than 0.
+    string constant INVALID_AMOUNT = "INVALID_AMOUNT";                                            // Amount must equal 1.
+}
diff --git a/packages/contracts/src/2.0.0/forwarder/mixins/MAssets.sol b/packages/contracts/src/2.0.0/forwarder/mixins/MAssets.sol
new file mode 100644
index 000000000..340ee0bcb
--- /dev/null
+++ b/packages/contracts/src/2.0.0/forwarder/mixins/MAssets.sol
@@ -0,0 +1,54 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity 0.4.24;
+
+import "../interfaces/IAssets.sol";
+
+
+contract MAssets is
+    IAssets
+{
+
+    /// @dev Transfers given amount of asset to sender.
+    /// @param assetData Byte array encoded for the respective asset proxy.
+    /// @param amount Amount of asset to transfer to sender.
+    function transferPurchasedAssetToSender(
+        bytes memory assetData,
+        uint256 amount
+    )
+        internal;
+
+    /// @dev Decodes ERC20 assetData and transfers given amount to sender.
+    /// @param assetData Byte array encoded for the respective asset proxy.
+    /// @param amount Amount of asset to transfer to sender.
+    function transferERC20Token(
+        bytes memory assetData,
+        uint256 amount
+    )
+        internal;
+
+    /// @dev Decodes ERC721 assetData and transfers given amount to sender.
+    /// @param assetData Byte array encoded for the respective asset proxy.
+    /// @param amount Amount of asset to transfer to sender.
+    function transferERC721Token(
+        bytes memory assetData,
+        uint256 amount
+    )
+        internal;
+}
diff --git a/packages/contracts/src/2.0.0/forwarder/mixins/MConstants.sol b/packages/contracts/src/2.0.0/forwarder/mixins/MConstants.sol
deleted file mode 100644
index 348bf169e..000000000
--- a/packages/contracts/src/2.0.0/forwarder/mixins/MConstants.sol
+++ /dev/null
@@ -1,35 +0,0 @@
-/*
-
-  Copyright 2018 ZeroEx Intl.
-
-  Licensed under the Apache License, Version 2.0 (the "License");
-  you may not use this file except in compliance with the License.
-  You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-  Unless required by applicable law or agreed to in writing, software
-  distributed under the License is distributed on an "AS IS" BASIS,
-  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-  See the License for the specific language governing permissions and
-  limitations under the License.
-
-*/
-
-pragma solidity 0.4.24;
-
-import "../../protocol/Exchange/interfaces/IExchange.sol";
-import "../../tokens/EtherToken/IEtherToken.sol";
-import "../../tokens/ERC20Token/IERC20Token.sol";
-
-
-contract MConstants {
-
-    // solhint-disable var-name-mixedcase
-    IExchange internal EXCHANGE;
-    IEtherToken internal ETHER_TOKEN;
-    IERC20Token internal ZRX_TOKEN;
-    bytes internal ZRX_ASSET_DATA;
-    bytes internal WETH_ASSET_DATA;
-    // solhint-enable var-name-mixedcase
-}
diff --git a/packages/contracts/src/2.0.0/forwarder/mixins/MExchangeWrapper.sol b/packages/contracts/src/2.0.0/forwarder/mixins/MExchangeWrapper.sol
new file mode 100644
index 000000000..5a2def7e5
--- /dev/null
+++ b/packages/contracts/src/2.0.0/forwarder/mixins/MExchangeWrapper.sol
@@ -0,0 +1,87 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity 0.4.24;
+pragma experimental ABIEncoderV2;
+
+import "../../protocol/Exchange/libs/LibOrder.sol";
+import "../../protocol/Exchange/libs/LibFillResults.sol";
+
+
+contract MExchangeWrapper {
+
+    /// @dev Fills the input order.
+    ///      Returns false if the transaction would otherwise revert.
+    /// @param order Order struct containing order specifications.
+    /// @param takerAssetFillAmount Desired amount of takerAsset to sell.
+    /// @param signature Proof that order has been created by maker.
+    /// @return Amounts filled and fees paid by maker and taker.
+    function fillOrderNoThrow(
+        LibOrder.Order memory order,
+        uint256 takerAssetFillAmount,
+        bytes memory signature
+    )
+        internal
+        returns (LibFillResults.FillResults memory fillResults);
+
+    /// @dev Synchronously executes multiple calls of fillOrder until total amount of WETH has been sold by taker.
+    ///      Returns false if the transaction would otherwise revert.
+    /// @param orders Array of order specifications.
+    /// @param wethSellAmount Desired amount of WETH to sell.
+    /// @param signatures Proofs that orders have been signed by makers.
+    /// @return Amounts filled and fees paid by makers and taker.
+    function marketSellWeth(
+        LibOrder.Order[] memory orders,
+        uint256 wethSellAmount,
+        bytes[] memory signatures
+    )
+        internal
+        returns (LibFillResults.FillResults memory totalFillResults);
+
+    /// @dev Synchronously executes multiple fill orders in a single transaction until total amount is bought by taker.
+    ///      Returns false if the transaction would otherwise revert.
+    ///      The asset being sold by taker must always be WETH.
+    /// @param orders Array of order specifications.
+    /// @param makerAssetFillAmount Desired amount of makerAsset to buy.
+    /// @param signatures Proofs that orders have been signed by makers.
+    /// @return Amounts filled and fees paid by makers and taker.
+    function marketBuyWithWeth(
+        LibOrder.Order[] memory orders,
+        uint256 makerAssetFillAmount,
+        bytes[] memory signatures
+    )
+        internal
+        returns (LibFillResults.FillResults memory totalFillResults);
+
+    /// @dev Buys zrxBuyAmount of ZRX fee tokens, taking into account ZRX fees for each order. This will guarantee
+    ///      that at least zrxBuyAmount of ZRX is purchased (sometimes slightly over due to rounding issues).
+    ///      It is possible that a request to buy 200 ZRX will require purchasing 202 ZRX
+    ///      as 2 ZRX is required to purchase the 200 ZRX fee tokens. This guarantees at least 200 ZRX for future purchases.
+    ///      The asset being sold by taker must always be WETH. 
+    /// @param orders Array of order specifications containing ZRX as makerAsset and WETH as takerAsset.
+    /// @param zrxBuyAmount Desired amount of ZRX to buy.
+    /// @param signatures Proofs that orders have been created by makers.
+    /// @return totalFillResults Amounts filled and fees paid by maker and taker.
+    function marketBuyZrxWithWeth(
+        LibOrder.Order[] memory orders,
+        uint256 zrxBuyAmount,
+        bytes[] memory signatures
+    )
+        internal
+        returns (LibFillResults.FillResults memory totalFillResults);
+}
diff --git a/packages/contracts/src/2.0.0/forwarder/mixins/MExpectedResults.sol b/packages/contracts/src/2.0.0/forwarder/mixins/MExpectedResults.sol
deleted file mode 100644
index cf03bb32e..000000000
--- a/packages/contracts/src/2.0.0/forwarder/mixins/MExpectedResults.sol
+++ /dev/null
@@ -1,42 +0,0 @@
-/*
-
-  Copyright 2018 ZeroEx Intl.
-
-  Licensed under the Apache License, Version 2.0 (the "License");
-  you may not use this file except in compliance with the License.
-  You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-  Unless required by applicable law or agreed to in writing, software
-  distributed under the License is distributed on an "AS IS" BASIS,
-  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-  See the License for the specific language governing permissions and
-  limitations under the License.
-
-*/
-
-pragma solidity 0.4.24;
-pragma experimental ABIEncoderV2;
-
-import "../../protocol/Exchange/libs/LibFillResults.sol";
-import "../../protocol/Exchange/libs/LibOrder.sol";
-import "../interfaces/IExpectedResults.sol";
-
-
-contract MExpectedResults is
-    IExpectedResults
-{
-
-    /// @dev Simulates the 0x Exchange fillOrder validation and calculations, without performing any state changes.
-    /// @param order An Order struct containing order specifications.
-    /// @param takerAssetFillAmount A number representing the amount of this order to fill.
-    /// @return fillResults Amounts filled and fees paid by maker and taker.
-    function calculateFillResults(
-        LibOrder.Order memory order,
-        uint256 takerAssetFillAmount
-    )
-        internal
-        view
-        returns (LibFillResults.FillResults memory fillResults);
-}
diff --git a/packages/contracts/src/2.0.0/forwarder/mixins/MFees.sol b/packages/contracts/src/2.0.0/forwarder/mixins/MFees.sol
deleted file mode 100644
index f332637ea..000000000
--- a/packages/contracts/src/2.0.0/forwarder/mixins/MFees.sol
+++ /dev/null
@@ -1,63 +0,0 @@
-/*
-
-  Copyright 2018 ZeroEx Intl.
-
-  Licensed under the Apache License, Version 2.0 (the "License");
-  you may not use this file except in compliance with the License.
-  You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-  Unless required by applicable law or agreed to in writing, software
-  distributed under the License is distributed on an "AS IS" BASIS,
-  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-  See the License for the specific language governing permissions and
-  limitations under the License.
-
-*/
-
-pragma solidity 0.4.24;
-
-
-contract MFees {
-
-    /// @dev Pays the feeRecipient feeProportion of the total takerEthAmount, denominated in ETH
-    /// @param takerEthAmount The total amount that was transacted in WETH, fees are calculated from this value.
-    /// @param feeProportion The proportion of fees
-    /// @param feeRecipient The recipient of the fees
-    /// @return ethFeeAmount Amount of ETH paid to feeRecipient as fee.
-    function payEthFee(
-        uint256 takerEthAmount,
-        uint16 feeProportion,
-        address feeRecipient
-    )
-        internal
-        returns (uint256 ethFeeAmount);
-
-    /// @dev Withdraws the remaining WETH, deduct and pay fees from this amount based on the takerTokenAmount to the feeRecipient.
-    ///      If a user overpaid ETH initially, the fees are calculated from the amount traded and deducted from withdrawAmount.
-    ///      Any remaining ETH is sent back to the user.
-    /// @param ethWithdrawAmount The amount to withdraw from the WETH contract.
-    /// @param wethAmountSold The total amount that was transacted in WETH, fees are calculated from this value.
-    /// @param feeProportion The proportion of fees
-    /// @param feeRecipient The recipient of the fees
-    function withdrawPayAndDeductEthFee(
-        uint256 ethWithdrawAmount,
-        uint256 wethAmountSold,
-        uint16 feeProportion,
-        address feeRecipient
-    )
-        internal;
-
-    /// @dev Checks whether the amount of tokens sold against the amount of tokens requested
-    ///      is within a certain threshold. This ensures the caller gets a fair deal when
-    ///      performing any token fee abstraction. Threshold is 95%. If fee abstraction costs more than
-    ///      5% of the total transaction, we return false.
-    /// @param requestedSellAmount The amount the user requested, or sent in to a payable function
-    /// @param tokenAmountSold The amount of the token that was sold after fee abstraction
-    /// @return bool of whether this is within an acceptable threshold
-    function isAcceptableThreshold(uint256 requestedSellAmount, uint256 tokenAmountSold)
-        internal
-        pure
-        returns (bool);
-}
diff --git a/packages/contracts/src/2.0.0/forwarder/mixins/MForwarderCore.sol b/packages/contracts/src/2.0.0/forwarder/mixins/MForwarderCore.sol
index 4a54e76b1..0f5cd9c66 100644
--- a/packages/contracts/src/2.0.0/forwarder/mixins/MForwarderCore.sol
+++ b/packages/contracts/src/2.0.0/forwarder/mixins/MForwarderCore.sol
@@ -28,65 +28,15 @@ contract MForwarderCore is
     IForwarderCore
 {
 
-    /// @dev Market sells WETH for ERC20 tokens.
-    /// @param orders An array of Order struct containing order specifications.
-    /// @param signatures An array of Proof that order has been created by maker.
-    /// @param feeOrders An array of Order struct containing order specifications for fees.
-    /// @param feeSignatures An array of Proof that order has been created by maker for the fee orders.
-    /// @param wethSellAmount The amount of WETH to sell.
-    /// @return FillResults amounts filled and fees paid by maker and taker.
-    function marketSellEthForERC20Internal(
-        LibOrder.Order[] memory orders,
-        bytes[] memory signatures,
-        LibOrder.Order[] memory feeOrders,
-        bytes[] memory feeSignatures,
-        uint256 wethSellAmount
+    /// @dev Ensures that all ZRX fees have been repurchased and no extra WETH owned by this contract has been sold.
+    /// @param orderFillResults Amounts filled and fees paid for primary orders.
+    /// @param feeOrderFillResults Amounts filled and fees paid for fee orders.
+    /// @param zrxBuyAmount The amount of ZRX that needed to be repurchased after filling primary orders.
+    function assertValidFillResults(
+        LibFillResults.FillResults memory orderFillResults,
+        LibFillResults.FillResults memory feeOrderFillResults,
+        uint256 zrxBuyAmount
     )
         internal
-        returns (LibFillResults.FillResults memory totalFillResults);
-
-    /// @dev Market sells WETH for ZRX tokens.
-    /// @param orders An array of Order struct containing order specifications.
-    /// @param signatures An array of Proof that order has been created by maker.
-    /// @param wethSellAmount The amount of WETH to sell.
-    /// @return FillResults amounts filled and fees paid by maker and taker.
-    function marketSellEthForZRXInternal(
-        LibOrder.Order[] memory orders,
-        bytes[] memory signatures,
-        uint256 wethSellAmount
-    )
-        internal
-        returns (LibFillResults.FillResults memory totalFillResults);
-
-    /// @dev Buys an exact amount of an ERC20 token using WETH.
-    /// @param orders Orders to fill. The maker asset is the ERC20 token to buy. The taker asset is WETH.
-    /// @param signatures Proof that the orders were created by their respective makers.
-    /// @param feeOrders to fill. The maker asset is ZRX and the taker asset is WETH.
-    /// @param feeSignatures Proof that the feeOrders were created by their respective makers.
-    /// @param makerTokenFillAmount Amount of the ERC20 token to buy.
-    /// @return totalFillResults Aggregated fill results of buying the ERC20 and ZRX tokens.
-    function marketBuyERC20TokensInternal(
-        LibOrder.Order[] memory orders,
-        bytes[] memory signatures,
-        LibOrder.Order[] memory feeOrders,
-        bytes[] memory feeSignatures,
-        uint256 makerTokenFillAmount
-    )
-        internal
-        returns (LibFillResults.FillResults memory totalFillResults);
-
-    /// @dev Buys an all of the ERC721 tokens in the orders.
-    /// @param orders Orders to fill. The maker asset is the ERC721 token to buy. The taker asset is WETH.
-    /// @param signatures Proof that the orders were created by their respective makers.
-    /// @param feeOrders to fill. The maker asset is ZRX and the taker asset is WETH.
-    /// @param feeSignatures Proof that the feeOrders were created by their respective makers.
-    /// @return totalFillResults Aggregated fill results of buying the ERC721 tokens and ZRX tokens.
-    function batchBuyERC721TokensInternal(
-        LibOrder.Order[] memory orders,
-        bytes[] memory signatures,
-        LibOrder.Order[] memory feeOrders,
-        bytes[] memory feeSignatures
-    )
-        internal
-        returns (LibFillResults.FillResults memory totalFillResults);
+        view;
 }
diff --git a/packages/contracts/src/2.0.0/forwarder/mixins/MMarketBuyZrx.sol b/packages/contracts/src/2.0.0/forwarder/mixins/MMarketBuyZrx.sol
deleted file mode 100644
index 3501ef001..000000000
--- a/packages/contracts/src/2.0.0/forwarder/mixins/MMarketBuyZrx.sol
+++ /dev/null
@@ -1,42 +0,0 @@
-/*
-
-  Copyright 2018 ZeroEx Intl.
-
-  Licensed under the Apache License, Version 2.0 (the "License");
-  you may not use this file except in compliance with the License.
-  You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-  Unless required by applicable law or agreed to in writing, software
-  distributed under the License is distributed on an "AS IS" BASIS,
-  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-  See the License for the specific language governing permissions and
-  limitations under the License.
-
-*/
-
-pragma solidity 0.4.24;
-
-import "../../protocol/Exchange/libs/LibFillResults.sol";
-import "../../protocol/Exchange/libs/LibOrder.sol";
-
-
-contract MMarketBuyZrx {
-
-    /// @dev Buys zrxBuyAmount of ZRX fee tokens, taking into account the fees on buying fee tokens. This will guarantee
-    ///      At least zrxBuyAmount of ZRX fee tokens are purchased (sometimes slightly over due to rounding issues).
-    ///      It is possible that a request to buy 200 ZRX fee tokens will require purchasing 202 ZRX tokens
-    ///      As 2 ZRX is required to purchase the 200 ZRX fee tokens. This guarantees at least 200 ZRX for future purchases.
-    /// @param orders An array of Order struct containing order specifications for fees.
-    /// @param signatures An array of Proof that order has been created by maker for the fee orders.
-    /// @param zrxBuyAmount The number of requested ZRX fee tokens.
-    /// @return totalFillResults Amounts filled and fees paid by maker and taker. makerTokenAmount is the zrx amount deducted of fees
-    function marketBuyZrxInternal(
-        LibOrder.Order[] memory orders,
-        bytes[] memory signatures,
-        uint256 zrxBuyAmount
-    )
-        internal
-        returns (LibFillResults.FillResults memory totalFillResults);
-}
diff --git a/packages/contracts/src/2.0.0/forwarder/mixins/MWeth.sol b/packages/contracts/src/2.0.0/forwarder/mixins/MWeth.sol
new file mode 100644
index 000000000..88e77be4e
--- /dev/null
+++ b/packages/contracts/src/2.0.0/forwarder/mixins/MWeth.sol
@@ -0,0 +1,41 @@
+/*
+
+  Copyright 2018 ZeroEx Intl.
+
+  Licensed under the Apache License, Version 2.0 (the "License");
+  you may not use this file except in compliance with the License.
+  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing, software
+  distributed under the License is distributed on an "AS IS" BASIS,
+  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  See the License for the specific language governing permissions and
+  limitations under the License.
+
+*/
+
+pragma solidity 0.4.24;
+
+
+contract MWeth {
+
+    /// @dev Converts message call's ETH value into WETH.
+    function convertEthToWeth()
+        internal;
+
+    /// @dev Transfers feePercentage of WETH spent on primary orders to feeRecipient.
+    ///      Refunds any excess ETH to msg.sender.
+    /// @param wethSoldExcludingFeeOrders Amount of WETH sold when filling primary orders.
+    /// @param wethSoldForZrx Amount of WETH sold when purchasing ZRX required for primary order fees.
+    /// @param feePercentage Percentage of WETH sold that will payed as fee to forwarding contract feeRecipient.
+    /// @param feeRecipient Address that will receive ETH when orders are filled.
+    function transferEthFeeAndRefund(
+        uint256 wethSoldExcludingFeeOrders,
+        uint256 wethSoldForZrx,
+        uint256 feePercentage,
+        address feeRecipient
+    )
+        internal;
+}
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/MixinWrapperFunctions.sol b/packages/contracts/src/2.0.0/protocol/Exchange/MixinWrapperFunctions.sol
index 567f26c52..86194f461 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/MixinWrapperFunctions.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/MixinWrapperFunctions.sol
@@ -32,6 +32,7 @@ contract MixinWrapperFunctions is
     LibAbiEncoder,
     MExchangeCore
 {
+
     /// @dev Fills the input order. Reverts if exact takerAssetFillAmount not filled.
     /// @param order Order struct containing order specifications.
     /// @param takerAssetFillAmount Desired amount of takerAsset to sell.
@@ -56,7 +57,7 @@ contract MixinWrapperFunctions is
         return fillResults;
     }
 
-    /// @dev Fills an order with specified parameters and ECDSA signature.
+    /// @dev Fills the input order.
     ///      Returns false if the transaction would otherwise revert.
     /// @param order Order struct containing order specifications.
     /// @param takerAssetFillAmount Desired amount of takerAsset to sell.
@@ -118,7 +119,8 @@ contract MixinWrapperFunctions is
         public
         returns (FillResults memory totalFillResults)
     {
-        for (uint256 i = 0; i < orders.length; i++) {
+        uint256 ordersLength = orders.length;
+        for (uint256 i = 0; i != ordersLength; i++) {
             FillResults memory singleFillResults = fillOrder(
                 orders[i],
                 takerAssetFillAmounts[i],
@@ -143,7 +145,8 @@ contract MixinWrapperFunctions is
         public
         returns (FillResults memory totalFillResults)
     {
-        for (uint256 i = 0; i < orders.length; i++) {
+        uint256 ordersLength = orders.length;
+        for (uint256 i = 0; i != ordersLength; i++) {
             FillResults memory singleFillResults = fillOrKillOrder(
                 orders[i],
                 takerAssetFillAmounts[i],
@@ -169,7 +172,8 @@ contract MixinWrapperFunctions is
         public
         returns (FillResults memory totalFillResults)
     {
-        for (uint256 i = 0; i < orders.length; i++) {
+        uint256 ordersLength = orders.length;
+        for (uint256 i = 0; i != ordersLength; i++) {
             FillResults memory singleFillResults = fillOrderNoThrow(
                 orders[i],
                 takerAssetFillAmounts[i],
@@ -195,7 +199,8 @@ contract MixinWrapperFunctions is
     {
         bytes memory takerAssetData = orders[0].takerAssetData;
     
-        for (uint256 i = 0; i < orders.length; i++) {
+        uint256 ordersLength = orders.length;
+        for (uint256 i = 0; i != ordersLength; i++) {
 
             // We assume that asset being sold by taker is the same for each order.
             // Rather than passing this in as calldata, we use the takerAssetData from the first order in all later orders.
@@ -215,7 +220,7 @@ contract MixinWrapperFunctions is
             addFillResults(totalFillResults, singleFillResults);
 
             // Stop execution if the entire amount of takerAsset has been sold
-            if (totalFillResults.takerAssetFilledAmount == takerAssetFillAmount) {
+            if (totalFillResults.takerAssetFilledAmount >= takerAssetFillAmount) {
                 break;
             }
         }
@@ -238,7 +243,8 @@ contract MixinWrapperFunctions is
     {
         bytes memory takerAssetData = orders[0].takerAssetData;
 
-        for (uint256 i = 0; i < orders.length; i++) {
+        uint256 ordersLength = orders.length;
+        for (uint256 i = 0; i != ordersLength; i++) {
 
             // We assume that asset being sold by taker is the same for each order.
             // Rather than passing this in as calldata, we use the takerAssetData from the first order in all later orders.
@@ -258,7 +264,7 @@ contract MixinWrapperFunctions is
             addFillResults(totalFillResults, singleFillResults);
 
             // Stop execution if the entire amount of takerAsset has been sold
-            if (totalFillResults.takerAssetFilledAmount == takerAssetFillAmount) {
+            if (totalFillResults.takerAssetFilledAmount >= takerAssetFillAmount) {
                 break;
             }
         }
@@ -280,7 +286,8 @@ contract MixinWrapperFunctions is
     {
         bytes memory makerAssetData = orders[0].makerAssetData;
 
-        for (uint256 i = 0; i < orders.length; i++) {
+        uint256 ordersLength = orders.length;
+        for (uint256 i = 0; i != ordersLength; i++) {
 
             // We assume that asset being bought by taker is the same for each order.
             // Rather than passing this in as calldata, we copy the makerAssetData from the first order onto all later orders.
@@ -308,7 +315,7 @@ contract MixinWrapperFunctions is
             addFillResults(totalFillResults, singleFillResults);
 
             // Stop execution if the entire amount of makerAsset has been bought
-            if (totalFillResults.makerAssetFilledAmount == makerAssetFillAmount) {
+            if (totalFillResults.makerAssetFilledAmount >= makerAssetFillAmount) {
                 break;
             }
         }
@@ -331,7 +338,8 @@ contract MixinWrapperFunctions is
     {
         bytes memory makerAssetData = orders[0].makerAssetData;
 
-        for (uint256 i = 0; i < orders.length; i++) {
+        uint256 ordersLength = orders.length;
+        for (uint256 i = 0; i != ordersLength; i++) {
 
             // We assume that asset being bought by taker is the same for each order.
             // Rather than passing this in as calldata, we copy the makerAssetData from the first order onto all later orders.
@@ -359,7 +367,7 @@ contract MixinWrapperFunctions is
             addFillResults(totalFillResults, singleFillResults);
 
             // Stop execution if the entire amount of makerAsset has been bought
-            if (totalFillResults.makerAssetFilledAmount == makerAssetFillAmount) {
+            if (totalFillResults.makerAssetFilledAmount >= makerAssetFillAmount) {
                 break;
             }
         }
@@ -371,7 +379,8 @@ contract MixinWrapperFunctions is
     function batchCancelOrders(LibOrder.Order[] memory orders)
         public
     {
-        for (uint256 i = 0; i < orders.length; i++) {
+        uint256 ordersLength = orders.length;
+        for (uint256 i = 0; i != ordersLength; i++) {
             cancelOrder(orders[i]);
         }
     }
@@ -384,9 +393,9 @@ contract MixinWrapperFunctions is
         view
         returns (LibOrder.OrderInfo[] memory)
     {
-        uint256 length = orders.length;
-        LibOrder.OrderInfo[] memory ordersInfo = new LibOrder.OrderInfo[](length);
-        for (uint256 i = 0; i < length; i++) {
+        uint256 ordersLength = orders.length;
+        LibOrder.OrderInfo[] memory ordersInfo = new LibOrder.OrderInfo[](ordersLength);
+        for (uint256 i = 0; i != ordersLength; i++) {
             ordersInfo[i] = getOrderInfo(orders[i]);
         }
         return ordersInfo;
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibMath.sol b/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibMath.sol
index 46c13d390..fa09da6ac 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibMath.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibMath.sol
@@ -33,7 +33,8 @@ contract LibMath is
     function getPartialAmount(
         uint256 numerator,
         uint256 denominator,
-        uint256 target)
+        uint256 target
+    )
         internal
         pure
         returns (uint256 partialAmount)
@@ -53,7 +54,8 @@ contract LibMath is
     function isRoundingError(
         uint256 numerator,
         uint256 denominator,
-        uint256 target)
+        uint256 target
+    )
         internal
         pure
         returns (bool isError)
diff --git a/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibOrder.sol b/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibOrder.sol
index 68f2c8aed..4031ff26b 100644
--- a/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibOrder.sol
+++ b/packages/contracts/src/2.0.0/protocol/Exchange/libs/LibOrder.sol
@@ -103,20 +103,20 @@ contract LibOrder is
         bytes32 takerAssetDataHash = keccak256(order.takerAssetData);
 
         // Assembly for more efficiently computing:
-        //    keccak256(abi.encode(
-        //        order.makerAddress,
-        //        order.takerAddress,
-        //        order.feeRecipientAddress,
-        //        order.senderAddress,
-        //        order.makerAssetAmount,
-        //        order.takerAssetAmount,
-        //        order.makerFee,
-        //        order.takerFee,
-        //        order.expirationTimeSeconds,
-        //        order.salt,
-        //        keccak256(order.makerAssetData),
-        //        keccak256(order.takerAssetData)
-        //    ));
+        // keccak256(abi.encode(
+        //     order.makerAddress,
+        //     order.takerAddress,
+        //     order.feeRecipientAddress,
+        //     order.senderAddress,
+        //     order.makerAssetAmount,
+        //     order.takerAssetAmount,
+        //     order.makerFee,
+        //     order.takerFee,
+        //     order.expirationTimeSeconds,
+        //     order.salt,
+        //     keccak256(order.makerAssetData),
+        //     keccak256(order.takerAssetData)
+        // ));
 
         assembly {
             // Backup
diff --git a/packages/contracts/src/2.0.0/utils/SafeMath/SafeMath.sol b/packages/contracts/src/2.0.0/utils/SafeMath/SafeMath.sol
index 190989181..63a2a085f 100644
--- a/packages/contracts/src/2.0.0/utils/SafeMath/SafeMath.sol
+++ b/packages/contracts/src/2.0.0/utils/SafeMath/SafeMath.sol
@@ -34,7 +34,7 @@ contract SafeMath {
     {
         require(
             b <= a,
-            "UINT256_OVERFLOW"
+            "UINT256_UNDERFLOW"
         );
         return a - b;
     }
diff --git a/packages/contracts/test/forwarder/forwarder.ts b/packages/contracts/test/forwarder/forwarder.ts
index 0256d7d81..19639d3aa 100644
--- a/packages/contracts/test/forwarder/forwarder.ts
+++ b/packages/contracts/test/forwarder/forwarder.ts
@@ -18,7 +18,6 @@ import { constants } from '../utils/constants';
 import { ERC20Wrapper } from '../utils/erc20_wrapper';
 import { ERC721Wrapper } from '../utils/erc721_wrapper';
 import { ExchangeWrapper } from '../utils/exchange_wrapper';
-import { formatters } from '../utils/formatters';
 import { ForwarderWrapper } from '../utils/forwarder_wrapper';
 import { OrderFactory } from '../utils/order_factory';
 import { ContractName, ERC20BalancesByOwner } from '../utils/types';
@@ -28,8 +27,7 @@ chaiSetup.configure();
 const expect = chai.expect;
 const blockchainLifecycle = new BlockchainLifecycle(web3Wrapper);
 const DECIMALS_DEFAULT = 18;
-// Set a gasPrice so when checking balance of msg.sender we can accurately calculate gasPrice*gasUsed
-const DEFAULT_GAS_PRICE = new BigNumber(1);
+const MAX_WETH_FILL_PERCENTAGE = 95;
 
 describe(ContractName.Forwarder, () => {
     let makerAddress: string;
@@ -47,25 +45,28 @@ describe(ContractName.Forwarder, () => {
     let forwarderWrapper: ForwarderWrapper;
     let exchangeWrapper: ExchangeWrapper;
 
-    let signedOrder: SignedOrder;
-    let signedOrders: SignedOrder[];
+    let orderWithoutFee: SignedOrder;
     let orderWithFee: SignedOrder;
-    let signedOrdersWithFee: SignedOrder[];
     let feeOrder: SignedOrder;
-    let feeOrders: SignedOrder[];
     let orderFactory: OrderFactory;
     let erc20Wrapper: ERC20Wrapper;
     let erc20Balances: ERC20BalancesByOwner;
     let tx: TransactionReceiptWithDecodedLogs;
 
     let erc721MakerAssetIds: BigNumber[];
-    let feeProportion: number = 0;
+    let takerEthBalanceBefore: BigNumber;
+    let feePercentage: BigNumber;
+    let gasPrice: BigNumber;
 
     before(async () => {
         await blockchainLifecycle.startAsync();
         const accounts = await web3Wrapper.getAvailableAddressesAsync();
         const usedAddresses = ([owner, makerAddress, takerAddress, feeRecipientAddress, otherAddress] = accounts);
 
+        const txHash = await web3Wrapper.sendTransactionAsync({ from: accounts[0], to: accounts[0], value: 0 });
+        const transaction = await web3Wrapper.getTransactionByHashAsync(txHash);
+        gasPrice = new BigNumber(transaction.gasPrice);
+
         const erc721Wrapper = new ERC721Wrapper(provider, usedAddresses, owner);
         erc20Wrapper = new ERC20Wrapper(provider, usedAddresses, owner);
 
@@ -135,681 +136,865 @@ describe(ContractName.Forwarder, () => {
             wethAssetData,
         );
         forwarderContract = new ForwarderContract(forwarderInstance.abi, forwarderInstance.address, provider);
-        forwarderWrapper = new ForwarderWrapper(forwarderContract, provider, zrxToken.address);
+        forwarderWrapper = new ForwarderWrapper(forwarderContract, provider);
+        const zrxDepositAmount = Web3Wrapper.toBaseUnitAmount(new BigNumber(10000), 18);
+        await web3Wrapper.awaitTransactionSuccessAsync(
+            await zrxToken.transfer.sendTransactionAsync(forwarderContract.address, zrxDepositAmount),
+        );
         erc20Wrapper.addTokenOwnerAddress(forwarderInstance.address);
-
-        web3Wrapper.abiDecoder.addABI(forwarderContract.abi);
-        web3Wrapper.abiDecoder.addABI(exchangeInstance.abi);
     });
     after(async () => {
         await blockchainLifecycle.revertAsync();
     });
     beforeEach(async () => {
         await blockchainLifecycle.startAsync();
-        feeProportion = 0;
         erc20Balances = await erc20Wrapper.getBalancesAsync();
-        signedOrder = await orderFactory.newSignedOrderAsync();
-        signedOrders = [signedOrder];
+        takerEthBalanceBefore = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
+        orderWithoutFee = await orderFactory.newSignedOrderAsync();
         feeOrder = await orderFactory.newSignedOrderAsync({
             makerAssetData: assetDataUtils.encodeERC20AssetData(zrxToken.address),
             takerFee: Web3Wrapper.toBaseUnitAmount(new BigNumber(1), DECIMALS_DEFAULT),
         });
-        feeOrders = [feeOrder];
         orderWithFee = await orderFactory.newSignedOrderAsync({
             takerFee: Web3Wrapper.toBaseUnitAmount(new BigNumber(1), DECIMALS_DEFAULT),
         });
-        signedOrdersWithFee = [orderWithFee];
     });
     afterEach(async () => {
         await blockchainLifecycle.revertAsync();
     });
-    describe('calculations', () => {
-        it('throws if partially filled orders passed in are not enough to satisfy requested amount', async () => {
-            feeOrders = [feeOrder];
-            const makerTokenFillAmount = feeOrder.makerAssetAmount.div(2);
-            const fillAmountWei = await forwarderWrapper.calculateMarketBuyFillAmountWeiAsync(
-                feeOrders,
-                [],
-                feeProportion,
-                makerTokenFillAmount,
-            );
-            // Fill the feeOrder
-            tx = await forwarderWrapper.marketBuyTokensWithEthAsync(feeOrders, [], makerTokenFillAmount, {
+
+    describe('marketSellOrdersWithEth without extra fees', () => {
+        it('should fill a single order', async () => {
+            const ordersWithoutFee = [orderWithoutFee];
+            const feeOrders: SignedOrder[] = [];
+            const ethValue = orderWithoutFee.takerAssetAmount.dividedToIntegerBy(2);
+
+            tx = await forwarderWrapper.marketSellOrdersWithEthAsync(ordersWithoutFee, feeOrders, {
+                value: ethValue,
                 from: takerAddress,
-                value: fillAmountWei,
             });
-            return expect(
-                forwarderWrapper.calculateMarketBuyFillAmountWeiAsync(
-                    feeOrders,
-                    [],
-                    feeProportion,
-                    makerTokenFillAmount,
-                ),
-            ).to.be.rejectedWith('Unable to satisfy makerAssetFillAmount with provided orders');
+            const takerEthBalanceAfter = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
+            const forwarderEthBalance = await web3Wrapper.getBalanceInWeiAsync(forwarderContract.address);
+            const newBalances = await erc20Wrapper.getBalancesAsync();
+
+            const primaryTakerAssetFillAmount = ForwarderWrapper.getPercentageOfValue(
+                ethValue,
+                MAX_WETH_FILL_PERCENTAGE,
+            );
+            const makerAssetFillAmount = primaryTakerAssetFillAmount
+                .times(orderWithoutFee.makerAssetAmount)
+                .dividedToIntegerBy(orderWithoutFee.takerAssetAmount);
+            const totalEthSpent = primaryTakerAssetFillAmount.plus(gasPrice.times(tx.gasUsed));
+
+            expect(takerEthBalanceAfter).to.be.bignumber.equal(takerEthBalanceBefore.minus(totalEthSpent));
+            expect(newBalances[makerAddress][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][defaultMakerAssetAddress].minus(makerAssetFillAmount),
+            );
+            expect(newBalances[takerAddress][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                erc20Balances[takerAddress][defaultMakerAssetAddress].plus(makerAssetFillAmount),
+            );
+            expect(newBalances[makerAddress][weth.address]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][weth.address].plus(primaryTakerAssetFillAmount),
+            );
+            expect(newBalances[forwarderContract.address][weth.address]).to.be.bignumber.equal(constants.ZERO_AMOUNT);
+            expect(newBalances[forwarderContract.address][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                constants.ZERO_AMOUNT,
+            );
+            expect(forwarderEthBalance).to.be.bignumber.equal(constants.ZERO_AMOUNT);
         });
-        it('throws if orders passed are cancelled', async () => {
-            tx = await exchangeWrapper.cancelOrderAsync(feeOrder, makerAddress);
-            // Cancel the feeOrder
-            return expect(
-                forwarderWrapper.calculateMarketBuyFillAmountWeiAsync(
-                    feeOrders,
-                    [],
-                    feeProportion,
-                    feeOrder.makerAssetAmount.div(2),
-                ),
-            ).to.be.rejectedWith('Unable to satisfy makerAssetFillAmount with provided orders');
+        it('should fill multiple orders', async () => {
+            const secondOrderWithoutFee = await orderFactory.newSignedOrderAsync();
+            const ordersWithoutFee = [orderWithoutFee, secondOrderWithoutFee];
+            const feeOrders: SignedOrder[] = [];
+            const ethValue = ordersWithoutFee[0].takerAssetAmount.plus(
+                ordersWithoutFee[1].takerAssetAmount.dividedToIntegerBy(2),
+            );
+
+            tx = await forwarderWrapper.marketSellOrdersWithEthAsync(ordersWithoutFee, feeOrders, {
+                value: ethValue,
+                from: takerAddress,
+            });
+            const takerEthBalanceAfter = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
+            const forwarderEthBalance = await web3Wrapper.getBalanceInWeiAsync(forwarderContract.address);
+            const newBalances = await erc20Wrapper.getBalancesAsync();
+
+            const primaryTakerAssetFillAmount = ForwarderWrapper.getPercentageOfValue(
+                ethValue,
+                MAX_WETH_FILL_PERCENTAGE,
+            );
+            const firstTakerAssetFillAmount = ordersWithoutFee[0].takerAssetAmount;
+            const secondTakerAssetFillAmount = primaryTakerAssetFillAmount.minus(firstTakerAssetFillAmount);
+
+            const makerAssetFillAmount = ordersWithoutFee[0].makerAssetAmount.plus(
+                ordersWithoutFee[1].makerAssetAmount
+                    .times(secondTakerAssetFillAmount)
+                    .dividedToIntegerBy(ordersWithoutFee[1].takerAssetAmount),
+            );
+            const totalEthSpent = primaryTakerAssetFillAmount.plus(gasPrice.times(tx.gasUsed));
+            expect(takerEthBalanceAfter).to.be.bignumber.equal(takerEthBalanceBefore.minus(totalEthSpent));
+            expect(newBalances[makerAddress][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][defaultMakerAssetAddress].minus(makerAssetFillAmount),
+            );
+            expect(newBalances[takerAddress][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                erc20Balances[takerAddress][defaultMakerAssetAddress].plus(makerAssetFillAmount),
+            );
+            expect(newBalances[makerAddress][weth.address]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][weth.address].plus(primaryTakerAssetFillAmount),
+            );
+            expect(newBalances[forwarderContract.address][weth.address]).to.be.bignumber.equal(constants.ZERO_AMOUNT);
+            expect(newBalances[forwarderContract.address][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                constants.ZERO_AMOUNT,
+            );
+            expect(forwarderEthBalance).to.be.bignumber.equal(constants.ZERO_AMOUNT);
         });
-    });
-    describe('marketSellEthForERC20 without extra fees', () => {
-        it('should fill the order', async () => {
-            const fillAmount = signedOrder.takerAssetAmount.div(2);
-            const makerBalanceBefore = erc20Balances[makerAddress][defaultMakerAssetAddress];
-            const takerBalanceBefore = erc20Balances[takerAddress][defaultMakerAssetAddress];
-            feeOrders = [];
-            tx = await forwarderWrapper.marketSellEthForERC20Async(signedOrders, feeOrders, {
-                value: fillAmount,
+        it('should fill the order and pay ZRX fees from a single feeOrder', async () => {
+            const ordersWithFee = [orderWithFee];
+            const feeOrders = [feeOrder];
+            const ethValue = orderWithFee.takerAssetAmount.dividedToIntegerBy(2);
+
+            tx = await forwarderWrapper.marketSellOrdersWithEthAsync(ordersWithFee, feeOrders, {
+                value: ethValue,
                 from: takerAddress,
             });
+            const takerEthBalanceAfter = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
+            const forwarderEthBalance = await web3Wrapper.getBalanceInWeiAsync(forwarderContract.address);
             const newBalances = await erc20Wrapper.getBalancesAsync();
-            const makerBalanceAfter = newBalances[makerAddress][defaultMakerAssetAddress];
-            const takerBalanceAfter = newBalances[takerAddress][defaultMakerAssetAddress];
-            const makerTokenFillAmount = fillAmount
-                .times(signedOrder.makerAssetAmount)
-                .dividedToIntegerBy(signedOrder.takerAssetAmount);
-
-            expect(makerBalanceAfter).to.be.bignumber.equal(makerBalanceBefore.minus(makerTokenFillAmount));
-            expect(takerBalanceAfter).to.be.bignumber.equal(takerBalanceBefore.plus(makerTokenFillAmount));
-            expect(newBalances[forwarderContract.address][weth.address]).to.be.bignumber.equal(new BigNumber(0));
+
+            const primaryTakerAssetFillAmount = ForwarderWrapper.getPercentageOfValue(
+                ethValue,
+                MAX_WETH_FILL_PERCENTAGE,
+            );
+            const makerAssetFillAmount = primaryTakerAssetFillAmount
+                .times(orderWithoutFee.makerAssetAmount)
+                .dividedToIntegerBy(orderWithoutFee.takerAssetAmount);
+            const feeAmount = ForwarderWrapper.getPercentageOfValue(
+                orderWithFee.takerFee.dividedToIntegerBy(2),
+                MAX_WETH_FILL_PERCENTAGE,
+            );
+            const wethSpentOnFeeOrders = ForwarderWrapper.getWethForFeeOrders(feeAmount, feeOrders);
+            const totalEthSpent = primaryTakerAssetFillAmount
+                .plus(wethSpentOnFeeOrders)
+                .plus(gasPrice.times(tx.gasUsed));
+
+            expect(takerEthBalanceAfter).to.be.bignumber.equal(takerEthBalanceBefore.minus(totalEthSpent));
+            expect(newBalances[makerAddress][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][defaultMakerAssetAddress].minus(makerAssetFillAmount),
+            );
+            expect(newBalances[takerAddress][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                erc20Balances[takerAddress][defaultMakerAssetAddress].plus(makerAssetFillAmount),
+            );
+            expect(newBalances[makerAddress][weth.address]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][weth.address].plus(primaryTakerAssetFillAmount).plus(wethSpentOnFeeOrders),
+            );
+            expect(newBalances[forwarderContract.address][weth.address]).to.be.bignumber.equal(constants.ZERO_AMOUNT);
+            expect(newBalances[forwarderContract.address][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                constants.ZERO_AMOUNT,
+            );
+            expect(forwarderEthBalance).to.be.bignumber.equal(constants.ZERO_AMOUNT);
         });
-        it('should fill the order and perform fee abstraction', async () => {
-            const fillAmount = signedOrder.takerAssetAmount.div(4);
-            const takerBalanceBefore = erc20Balances[takerAddress][defaultMakerAssetAddress];
-            tx = await forwarderWrapper.marketSellEthForERC20Async(signedOrdersWithFee, feeOrders, {
-                value: fillAmount,
+        it('should fill the orders and pay ZRX from multiple feeOrders', async () => {
+            const ordersWithFee = [orderWithFee];
+            const ethValue = orderWithFee.takerAssetAmount;
+            const makerAssetData = assetDataUtils.encodeERC20AssetData(zrxToken.address);
+            const makerAssetAmount = orderWithFee.takerFee.dividedToIntegerBy(2);
+            const takerAssetAmount = feeOrder.takerAssetAmount
+                .times(makerAssetAmount)
+                .dividedToIntegerBy(feeOrder.makerAssetAmount);
+
+            const firstFeeOrder = await orderFactory.newSignedOrderAsync({
+                makerAssetData,
+                makerAssetAmount,
+                takerAssetAmount,
+            });
+            const secondFeeOrder = await orderFactory.newSignedOrderAsync({
+                makerAssetData,
+                makerAssetAmount,
+                takerAssetAmount,
+            });
+            const feeOrders = [firstFeeOrder, secondFeeOrder];
+
+            tx = await forwarderWrapper.marketSellOrdersWithEthAsync(ordersWithFee, feeOrders, {
+                value: ethValue,
                 from: takerAddress,
             });
+            const takerEthBalanceAfter = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
+            const forwarderEthBalance = await web3Wrapper.getBalanceInWeiAsync(forwarderContract.address);
             const newBalances = await erc20Wrapper.getBalancesAsync();
-            const takerBalanceAfter = newBalances[takerAddress][defaultMakerAssetAddress];
 
-            const acceptPercentage = 98;
-            const acceptableThreshold = takerBalanceBefore.plus(fillAmount.times(acceptPercentage).dividedBy(100));
-            const isWithinThreshold = takerBalanceAfter.greaterThanOrEqualTo(acceptableThreshold);
-            expect(isWithinThreshold).to.be.true();
-            expect(newBalances[forwarderContract.address][weth.address]).to.be.bignumber.equal(new BigNumber(0));
+            const primaryTakerAssetFillAmount = ForwarderWrapper.getPercentageOfValue(
+                ethValue,
+                MAX_WETH_FILL_PERCENTAGE,
+            );
+            const makerAssetFillAmount = primaryTakerAssetFillAmount
+                .times(orderWithoutFee.makerAssetAmount)
+                .dividedToIntegerBy(orderWithoutFee.takerAssetAmount);
+            const feeAmount = ForwarderWrapper.getPercentageOfValue(orderWithFee.takerFee, MAX_WETH_FILL_PERCENTAGE);
+            const wethSpentOnFeeOrders = ForwarderWrapper.getWethForFeeOrders(feeAmount, feeOrders);
+            const totalEthSpent = primaryTakerAssetFillAmount
+                .plus(wethSpentOnFeeOrders)
+                .plus(gasPrice.times(tx.gasUsed));
+
+            expect(takerEthBalanceAfter).to.be.bignumber.equal(takerEthBalanceBefore.minus(totalEthSpent));
+            expect(newBalances[makerAddress][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][defaultMakerAssetAddress].minus(makerAssetFillAmount),
+            );
+            expect(newBalances[takerAddress][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                erc20Balances[takerAddress][defaultMakerAssetAddress].plus(makerAssetFillAmount),
+            );
+            expect(newBalances[makerAddress][weth.address]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][weth.address].plus(primaryTakerAssetFillAmount).plus(wethSpentOnFeeOrders),
+            );
+            expect(newBalances[forwarderContract.address][weth.address]).to.be.bignumber.equal(constants.ZERO_AMOUNT);
+            expect(newBalances[forwarderContract.address][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                constants.ZERO_AMOUNT,
+            );
+            expect(forwarderEthBalance).to.be.bignumber.equal(constants.ZERO_AMOUNT);
         });
         it('should fill the order when token is ZRX with fees', async () => {
             orderWithFee = await orderFactory.newSignedOrderAsync({
                 makerAssetData: assetDataUtils.encodeERC20AssetData(zrxToken.address),
                 takerFee: Web3Wrapper.toBaseUnitAmount(new BigNumber(1), DECIMALS_DEFAULT),
             });
-            signedOrdersWithFee = [orderWithFee];
-            feeOrders = [];
-            const fillAmount = signedOrder.takerAssetAmount.div(4);
-            const takerBalanceBefore = erc20Balances[takerAddress][zrxToken.address];
-            tx = await forwarderWrapper.marketSellEthForERC20Async(signedOrdersWithFee, feeOrders, {
-                value: fillAmount,
+            const ordersWithFee = [orderWithFee];
+            const feeOrders: SignedOrder[] = [];
+            const ethValue = orderWithFee.takerAssetAmount.dividedToIntegerBy(2);
+
+            tx = await forwarderWrapper.marketSellOrdersWithEthAsync(ordersWithFee, feeOrders, {
+                value: ethValue,
                 from: takerAddress,
             });
+            const takerEthBalanceAfter = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
+            const forwarderEthBalance = await web3Wrapper.getBalanceInWeiAsync(forwarderContract.address);
             const newBalances = await erc20Wrapper.getBalancesAsync();
-            const takerBalanceAfter = newBalances[takerAddress][zrxToken.address];
 
-            const acceptPercentage = 98;
-            const acceptableThreshold = takerBalanceBefore.plus(fillAmount.times(acceptPercentage).dividedBy(100));
-            const isWithinThreshold = takerBalanceAfter.greaterThanOrEqualTo(acceptableThreshold);
-            expect(isWithinThreshold).to.be.true();
-            expect(newBalances[forwarderContract.address][weth.address]).to.be.bignumber.equal(new BigNumber(0));
+            const makerAssetFillAmount = orderWithFee.makerAssetAmount.dividedToIntegerBy(2);
+            const totalEthSpent = ethValue.plus(gasPrice.times(tx.gasUsed));
+            const takerFeePaid = orderWithFee.takerFee.dividedToIntegerBy(2);
+            const makerFeePaid = orderWithFee.makerFee.dividedToIntegerBy(2);
+
+            expect(takerEthBalanceAfter).to.be.bignumber.equal(takerEthBalanceBefore.minus(totalEthSpent));
+            expect(newBalances[makerAddress][zrxToken.address]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][zrxToken.address].minus(makerAssetFillAmount).minus(makerFeePaid),
+            );
+            expect(newBalances[takerAddress][zrxToken.address]).to.be.bignumber.equal(
+                erc20Balances[takerAddress][zrxToken.address].plus(makerAssetFillAmount).minus(takerFeePaid),
+            );
+            expect(newBalances[makerAddress][weth.address]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][weth.address].plus(ethValue),
+            );
+            expect(newBalances[forwarderContract.address][weth.address]).to.be.bignumber.equal(constants.ZERO_AMOUNT);
+            expect(newBalances[forwarderContract.address][zrxToken.address]).to.be.bignumber.equal(
+                erc20Balances[forwarderContract.address][zrxToken.address],
+            );
+            expect(forwarderEthBalance).to.be.bignumber.equal(constants.ZERO_AMOUNT);
         });
-        it('should fail if sent an ETH amount too high', async () => {
-            signedOrder = await orderFactory.newSignedOrderAsync({
-                makerAssetData: assetDataUtils.encodeERC20AssetData(zrxToken.address),
-                takerFee: Web3Wrapper.toBaseUnitAmount(new BigNumber(1), DECIMALS_DEFAULT),
+        it('should refund remaining ETH if amount is greater than takerAssetAmount', async () => {
+            const ordersWithoutFee = [orderWithoutFee];
+            const feeOrders: SignedOrder[] = [];
+            const ethValue = orderWithoutFee.takerAssetAmount.times(2);
+
+            tx = await forwarderWrapper.marketSellOrdersWithEthAsync(ordersWithoutFee, feeOrders, {
+                value: ethValue,
+                from: takerAddress,
             });
-            const fillAmount = signedOrder.takerAssetAmount.times(2);
-            return expectTransactionFailedAsync(
-                forwarderWrapper.marketSellEthForERC20Async(signedOrdersWithFee, feeOrders, {
-                    value: fillAmount,
-                    from: takerAddress,
-                }),
-                RevertReason.UnacceptableThreshold,
-            );
+            const takerEthBalanceAfter = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
+            const totalEthSpent = orderWithoutFee.takerAssetAmount.plus(gasPrice.times(tx.gasUsed));
+
+            expect(takerEthBalanceAfter).to.be.bignumber.equal(takerEthBalanceBefore.minus(totalEthSpent));
         });
-        it('should fail if fee abstraction amount is too high', async () => {
+        it('should revert if ZRX cannot be fully repurchased', async () => {
             orderWithFee = await orderFactory.newSignedOrderAsync({
                 takerFee: Web3Wrapper.toBaseUnitAmount(new BigNumber(50), DECIMALS_DEFAULT),
             });
-            signedOrdersWithFee = [orderWithFee];
+            const ordersWithFee = [orderWithFee];
             feeOrder = await orderFactory.newSignedOrderAsync({
                 makerAssetData: assetDataUtils.encodeERC20AssetData(zrxToken.address),
                 makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(1), DECIMALS_DEFAULT),
             });
-            feeOrders = [feeOrder];
-            const fillAmount = signedOrder.takerAssetAmount.div(4);
+            const feeOrders = [feeOrder];
+            const ethValue = orderWithFee.takerAssetAmount;
             return expectTransactionFailedAsync(
-                forwarderWrapper.marketSellEthForERC20Async(signedOrdersWithFee, feeOrders, {
-                    value: fillAmount,
+                forwarderWrapper.marketSellOrdersWithEthAsync(ordersWithFee, feeOrders, {
+                    value: ethValue,
                     from: takerAddress,
                 }),
-                RevertReason.TransferFailed,
+                RevertReason.CompleteFillFailed,
             );
         });
-        it('throws when mixed ERC721 and ERC20 assets with ERC20 first', async () => {
+        it('should not fill orders with different makerAssetData than the first order', async () => {
             const makerAssetId = erc721MakerAssetIds[0];
             const erc721SignedOrder = await orderFactory.newSignedOrderAsync({
                 makerAssetAmount: new BigNumber(1),
                 makerAssetData: assetDataUtils.encodeERC721AssetData(erc721Token.address, makerAssetId),
             });
             const erc20SignedOrder = await orderFactory.newSignedOrderAsync();
-            signedOrders = [erc20SignedOrder, erc721SignedOrder];
-            const fillAmountWei = erc20SignedOrder.takerAssetAmount.plus(erc721SignedOrder.takerAssetAmount);
-            return expectTransactionFailedAsync(
-                forwarderWrapper.marketSellEthForERC20Async(signedOrders, feeOrders, {
-                    from: takerAddress,
-                    value: fillAmountWei,
-                }),
-                RevertReason.InvalidOrderSignature,
-            );
+            const ordersWithoutFee = [erc20SignedOrder, erc721SignedOrder];
+            const feeOrders: SignedOrder[] = [];
+            const ethValue = erc20SignedOrder.takerAssetAmount.plus(erc721SignedOrder.takerAssetAmount);
+
+            tx = await forwarderWrapper.marketSellOrdersWithEthAsync(ordersWithoutFee, feeOrders, {
+                value: ethValue,
+                from: takerAddress,
+            });
+            const takerEthBalanceAfter = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
+            const totalEthSpent = erc20SignedOrder.takerAssetAmount.plus(gasPrice.times(tx.gasUsed));
+
+            expect(takerEthBalanceAfter).to.be.bignumber.equal(takerEthBalanceBefore.minus(totalEthSpent));
         });
     });
-    describe('marketSellEthForERC20 with extra fees', () => {
-        it('should fill the order and send fee to fee recipient', async () => {
-            const initEthBalance = await web3Wrapper.getBalanceInWeiAsync(feeRecipientAddress);
-            const fillAmount = signedOrder.takerAssetAmount.div(2);
-            feeProportion = 150; // 1.5%
-            feeOrders = [];
-            tx = await forwarderWrapper.marketSellEthForERC20Async(
-                signedOrders,
+    describe('marketSellOrdersWithEth with extra fees', () => {
+        it('should fill the order and send fee to feeRecipient', async () => {
+            const ordersWithoutFee = [orderWithoutFee];
+            const feeOrders: SignedOrder[] = [];
+            const ethValue = orderWithoutFee.takerAssetAmount.div(2);
+
+            const baseFeePercentage = 2;
+            feePercentage = ForwarderWrapper.getPercentageOfValue(constants.PERCENTAGE_DENOMINATOR, baseFeePercentage);
+            const feeRecipientEthBalanceBefore = await web3Wrapper.getBalanceInWeiAsync(feeRecipientAddress);
+            tx = await forwarderWrapper.marketSellOrdersWithEthAsync(
+                ordersWithoutFee,
                 feeOrders,
                 {
+                    value: ethValue,
                     from: takerAddress,
-                    value: fillAmount,
-                    gasPrice: DEFAULT_GAS_PRICE,
-                },
-                {
-                    feeProportion,
-                    feeRecipient: feeRecipientAddress,
                 },
+                { feePercentage, feeRecipient: feeRecipientAddress },
             );
+            const takerEthBalanceAfter = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
+            const feeRecipientEthBalanceAfter = await web3Wrapper.getBalanceInWeiAsync(feeRecipientAddress);
+            const forwarderEthBalance = await web3Wrapper.getBalanceInWeiAsync(forwarderContract.address);
             const newBalances = await erc20Wrapper.getBalancesAsync();
-            const makerBalanceBefore = erc20Balances[makerAddress][defaultMakerAssetAddress];
-            const makerBalanceAfter = newBalances[makerAddress][defaultMakerAssetAddress];
-            const takerBalanceAfter = newBalances[takerAddress][defaultMakerAssetAddress];
-            const afterEthBalance = await web3Wrapper.getBalanceInWeiAsync(feeRecipientAddress);
-            const takerBoughtAmount = takerBalanceAfter.minus(erc20Balances[takerAddress][defaultMakerAssetAddress]);
 
-            expect(makerBalanceAfter).to.be.bignumber.equal(makerBalanceBefore.minus(takerBoughtAmount));
-            expect(afterEthBalance).to.be.bignumber.equal(
-                initEthBalance.plus(fillAmount.times(feeProportion).dividedBy(10000)),
+            const primaryTakerAssetFillAmount = ForwarderWrapper.getPercentageOfValue(
+                ethValue,
+                MAX_WETH_FILL_PERCENTAGE,
+            );
+            const makerAssetFillAmount = primaryTakerAssetFillAmount
+                .times(orderWithoutFee.makerAssetAmount)
+                .dividedToIntegerBy(orderWithoutFee.takerAssetAmount);
+            const ethSpentOnFee = ForwarderWrapper.getPercentageOfValue(primaryTakerAssetFillAmount, baseFeePercentage);
+            const totalEthSpent = primaryTakerAssetFillAmount.plus(ethSpentOnFee).plus(gasPrice.times(tx.gasUsed));
+
+            expect(takerEthBalanceAfter).to.be.bignumber.equal(takerEthBalanceBefore.minus(totalEthSpent));
+            expect(newBalances[makerAddress][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][defaultMakerAssetAddress].minus(makerAssetFillAmount),
             );
-            expect(newBalances[forwarderContract.address][weth.address]).to.be.bignumber.equal(new BigNumber(0));
+            expect(newBalances[takerAddress][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                erc20Balances[takerAddress][defaultMakerAssetAddress].plus(makerAssetFillAmount),
+            );
+            expect(newBalances[makerAddress][weth.address]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][weth.address].plus(primaryTakerAssetFillAmount),
+            );
+            expect(newBalances[forwarderContract.address][weth.address]).to.be.bignumber.equal(constants.ZERO_AMOUNT);
+            expect(newBalances[forwarderContract.address][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                constants.ZERO_AMOUNT,
+            );
+            expect(feeRecipientEthBalanceAfter).to.be.bignumber.equal(feeRecipientEthBalanceBefore.plus(ethSpentOnFee));
+            expect(forwarderEthBalance).to.be.bignumber.equal(constants.ZERO_AMOUNT);
         });
         it('should fail if the fee is set too high', async () => {
-            const initEthBalance = await web3Wrapper.getBalanceInWeiAsync(feeRecipientAddress);
-            const fillAmount = signedOrder.takerAssetAmount.div(2);
-            feeProportion = 1500; // 15.0%
-            feeOrders = [];
+            const ethValue = orderWithoutFee.takerAssetAmount.div(2);
+            const baseFeePercentage = 6;
+            feePercentage = ForwarderWrapper.getPercentageOfValue(ethValue, baseFeePercentage);
+            const ordersWithoutFee = [orderWithoutFee];
+            const feeOrders: SignedOrder[] = [];
             await expectTransactionFailedAsync(
-                forwarderWrapper.marketSellEthForERC20Async(
-                    signedOrders,
+                forwarderWrapper.marketSellOrdersWithEthAsync(
+                    ordersWithoutFee,
                     feeOrders,
-                    { from: takerAddress, value: fillAmount, gasPrice: DEFAULT_GAS_PRICE },
-                    { feeProportion, feeRecipient: feeRecipientAddress },
+                    { from: takerAddress, value: ethValue, gasPrice },
+                    { feePercentage, feeRecipient: feeRecipientAddress },
                 ),
-                RevertReason.FeeProportionTooLarge,
+                RevertReason.FeePercentageTooLarge,
+            );
+        });
+        it('should fail if there is not enough ETH remaining to pay the fee', async () => {
+            const ethValue = orderWithoutFee.takerAssetAmount.div(2);
+            const baseFeePercentage = 5;
+            feePercentage = ForwarderWrapper.getPercentageOfValue(constants.PERCENTAGE_DENOMINATOR, baseFeePercentage);
+            const ordersWithFee = [orderWithFee];
+            const feeOrders = [feeOrder];
+            await expectTransactionFailedAsync(
+                forwarderWrapper.marketSellOrdersWithEthAsync(
+                    ordersWithFee,
+                    feeOrders,
+                    { from: takerAddress, value: ethValue, gasPrice },
+                    { feePercentage, feeRecipient: feeRecipientAddress },
+                ),
+                RevertReason.InsufficientEthRemaining,
             );
-            const afterEthBalance = await web3Wrapper.getBalanceInWeiAsync(feeRecipientAddress);
-            expect(afterEthBalance).to.be.bignumber.equal(initEthBalance);
         });
     });
-    describe('marketBuyTokensWithEth', () => {
-        it('should buy the exact amount of assets', async () => {
-            const makerAssetAmount = signedOrder.makerAssetAmount.div(2);
-            const initEthBalance = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
-            const balancesBefore = await erc20Wrapper.getBalancesAsync();
-            const rate = signedOrder.makerAssetAmount.dividedBy(signedOrder.takerAssetAmount);
-            const fillAmountWei = makerAssetAmount.dividedToIntegerBy(rate);
-            feeOrders = [];
-            tx = await forwarderWrapper.marketBuyTokensWithEthAsync(signedOrders, feeOrders, makerAssetAmount, {
+    describe('marketBuyOrdersWithEth without extra fees', () => {
+        it('should buy the exact amount of makerAsset in a single order', async () => {
+            const ordersWithoutFee = [orderWithoutFee];
+            const feeOrders: SignedOrder[] = [];
+            const makerAssetFillAmount = orderWithoutFee.makerAssetAmount.dividedToIntegerBy(2);
+            const ethValue = orderWithoutFee.takerAssetAmount.dividedToIntegerBy(2);
+
+            tx = await forwarderWrapper.marketBuyOrdersWithEthAsync(ordersWithoutFee, feeOrders, makerAssetFillAmount, {
+                value: ethValue,
                 from: takerAddress,
-                value: fillAmountWei,
-                gasPrice: DEFAULT_GAS_PRICE,
             });
+            const takerEthBalanceAfter = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
+            const forwarderEthBalance = await web3Wrapper.getBalanceInWeiAsync(forwarderContract.address);
             const newBalances = await erc20Wrapper.getBalancesAsync();
-            const takerBalanceBefore = balancesBefore[takerAddress][defaultMakerAssetAddress];
-            const takerBalanceAfter = newBalances[takerAddress][defaultMakerAssetAddress];
-            const afterEthBalance = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
-            const expectedEthBalanceAfterGasCosts = initEthBalance.minus(fillAmountWei).minus(tx.gasUsed);
-            expect(takerBalanceAfter).to.be.bignumber.eq(takerBalanceBefore.plus(makerAssetAmount));
-            expect(afterEthBalance).to.be.bignumber.eq(expectedEthBalanceAfterGasCosts);
+
+            const primaryTakerAssetFillAmount = ethValue;
+            const totalEthSpent = primaryTakerAssetFillAmount.plus(gasPrice.times(tx.gasUsed));
+
+            expect(takerEthBalanceAfter).to.be.bignumber.equal(takerEthBalanceBefore.minus(totalEthSpent));
+            expect(newBalances[makerAddress][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][defaultMakerAssetAddress].minus(makerAssetFillAmount),
+            );
+            expect(newBalances[takerAddress][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                erc20Balances[takerAddress][defaultMakerAssetAddress].plus(makerAssetFillAmount),
+            );
+            expect(newBalances[makerAddress][weth.address]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][weth.address].plus(primaryTakerAssetFillAmount),
+            );
+            expect(newBalances[forwarderContract.address][weth.address]).to.be.bignumber.equal(constants.ZERO_AMOUNT);
+            expect(newBalances[forwarderContract.address][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                constants.ZERO_AMOUNT,
+            );
+            expect(forwarderEthBalance).to.be.bignumber.equal(constants.ZERO_AMOUNT);
         });
-        it('should buy the exact amount of assets and return excess ETH', async () => {
-            const makerAssetAmount = signedOrder.makerAssetAmount.div(2);
-            const initEthBalance = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
-            const balancesBefore = await erc20Wrapper.getBalancesAsync();
-            const rate = signedOrder.makerAssetAmount.dividedBy(signedOrder.takerAssetAmount);
-            const fillAmount = makerAssetAmount.dividedToIntegerBy(rate);
-            const excessFillAmount = fillAmount.times(2);
-            feeOrders = [];
-            tx = await forwarderWrapper.marketBuyTokensWithEthAsync(signedOrders, feeOrders, makerAssetAmount, {
+        it('should buy the exact amount of makerAsset in multiple orders', async () => {
+            const secondOrderWithoutFee = await orderFactory.newSignedOrderAsync();
+            const ordersWithoutFee = [orderWithoutFee, secondOrderWithoutFee];
+            const feeOrders: SignedOrder[] = [];
+            const makerAssetFillAmount = ordersWithoutFee[0].makerAssetAmount.plus(
+                ordersWithoutFee[1].makerAssetAmount.dividedToIntegerBy(2),
+            );
+            const ethValue = ordersWithoutFee[0].takerAssetAmount.plus(
+                ordersWithoutFee[1].takerAssetAmount.dividedToIntegerBy(2),
+            );
+
+            tx = await forwarderWrapper.marketBuyOrdersWithEthAsync(ordersWithoutFee, feeOrders, makerAssetFillAmount, {
+                value: ethValue,
                 from: takerAddress,
-                value: excessFillAmount,
-                gasPrice: DEFAULT_GAS_PRICE,
             });
+            const takerEthBalanceAfter = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
+            const forwarderEthBalance = await web3Wrapper.getBalanceInWeiAsync(forwarderContract.address);
             const newBalances = await erc20Wrapper.getBalancesAsync();
-            const takerBalanceBefore = balancesBefore[takerAddress][defaultMakerAssetAddress];
-            const takerBalanceAfter = newBalances[takerAddress][defaultMakerAssetAddress];
-            const afterEthBalance = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
-            const expectedEthBalanceAfterGasCosts = initEthBalance.minus(fillAmount).minus(tx.gasUsed);
-            expect(takerBalanceAfter).to.be.bignumber.eq(takerBalanceBefore.plus(makerAssetAmount));
-            expect(afterEthBalance).to.be.bignumber.eq(expectedEthBalanceAfterGasCosts);
+
+            const primaryTakerAssetFillAmount = ethValue;
+            const totalEthSpent = primaryTakerAssetFillAmount.plus(gasPrice.times(tx.gasUsed));
+
+            expect(takerEthBalanceAfter).to.be.bignumber.equal(takerEthBalanceBefore.minus(totalEthSpent));
+            expect(newBalances[makerAddress][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][defaultMakerAssetAddress].minus(makerAssetFillAmount),
+            );
+            expect(newBalances[takerAddress][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                erc20Balances[takerAddress][defaultMakerAssetAddress].plus(makerAssetFillAmount),
+            );
+            expect(newBalances[makerAddress][weth.address]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][weth.address].plus(primaryTakerAssetFillAmount),
+            );
+            expect(newBalances[forwarderContract.address][weth.address]).to.be.bignumber.equal(constants.ZERO_AMOUNT);
+            expect(newBalances[forwarderContract.address][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                constants.ZERO_AMOUNT,
+            );
+            expect(forwarderEthBalance).to.be.bignumber.equal(constants.ZERO_AMOUNT);
         });
-        it('should buy the exact amount of assets with fee abstraction', async () => {
-            const makerAssetAmount = signedOrder.makerAssetAmount.div(2);
-            const balancesBefore = await erc20Wrapper.getBalancesAsync();
-            const rate = signedOrder.makerAssetAmount.dividedBy(signedOrder.takerAssetAmount);
-            const fillAmount = makerAssetAmount.dividedToIntegerBy(rate);
-            const excessFillAmount = fillAmount.times(2);
-            tx = await forwarderWrapper.marketBuyTokensWithEthAsync(signedOrdersWithFee, feeOrders, makerAssetAmount, {
+        it('should buy the exact amount of makerAsset and return excess ETH', async () => {
+            const ordersWithoutFee = [orderWithoutFee];
+            const feeOrders: SignedOrder[] = [];
+            const makerAssetFillAmount = orderWithoutFee.makerAssetAmount.dividedToIntegerBy(2);
+            const ethValue = orderWithoutFee.takerAssetAmount;
+
+            tx = await forwarderWrapper.marketBuyOrdersWithEthAsync(ordersWithoutFee, feeOrders, makerAssetFillAmount, {
+                value: ethValue,
                 from: takerAddress,
-                value: excessFillAmount,
             });
+            const takerEthBalanceAfter = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
+            const forwarderEthBalance = await web3Wrapper.getBalanceInWeiAsync(forwarderContract.address);
             const newBalances = await erc20Wrapper.getBalancesAsync();
-            const takerBalanceBefore = balancesBefore[takerAddress][defaultMakerAssetAddress];
-            const takerBalanceAfter = newBalances[takerAddress][defaultMakerAssetAddress];
-            expect(takerBalanceAfter).to.be.bignumber.eq(takerBalanceBefore.plus(makerAssetAmount));
-        });
-        it('should buy the exact amount of assets when buying zrx with fee abstraction', async () => {
-            signedOrder = await orderFactory.newSignedOrderAsync({
-                makerAssetData: assetDataUtils.encodeERC20AssetData(zrxToken.address),
-                takerFee: Web3Wrapper.toBaseUnitAmount(new BigNumber(1), DECIMALS_DEFAULT),
-            });
-            signedOrdersWithFee = [signedOrder];
-            feeOrders = [];
-            const makerAssetAmount = signedOrder.makerAssetAmount.div(2);
-            const takerWeiBalanceBefore = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
-            const balancesBefore = await erc20Wrapper.getBalancesAsync();
-            const fillAmountWei = await forwarderWrapper.calculateMarketBuyFillAmountWeiAsync(
-                signedOrdersWithFee,
-                feeOrders,
-                feeProportion,
-                makerAssetAmount,
+
+            const primaryTakerAssetFillAmount = ethValue.dividedToIntegerBy(2);
+            const totalEthSpent = primaryTakerAssetFillAmount.plus(gasPrice.times(tx.gasUsed));
+
+            expect(takerEthBalanceAfter).to.be.bignumber.equal(takerEthBalanceBefore.minus(totalEthSpent));
+            expect(newBalances[makerAddress][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][defaultMakerAssetAddress].minus(makerAssetFillAmount),
+            );
+            expect(newBalances[takerAddress][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                erc20Balances[takerAddress][defaultMakerAssetAddress].plus(makerAssetFillAmount),
+            );
+            expect(newBalances[makerAddress][weth.address]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][weth.address].plus(primaryTakerAssetFillAmount),
             );
-            tx = await forwarderWrapper.marketBuyTokensWithEthAsync(signedOrdersWithFee, feeOrders, makerAssetAmount, {
+            expect(newBalances[forwarderContract.address][weth.address]).to.be.bignumber.equal(constants.ZERO_AMOUNT);
+            expect(newBalances[forwarderContract.address][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                constants.ZERO_AMOUNT,
+            );
+            expect(forwarderEthBalance).to.be.bignumber.equal(constants.ZERO_AMOUNT);
+        });
+        it('should buy the exact amount of makerAsset and pay ZRX from feeOrders', async () => {
+            const ordersWithFee = [orderWithFee];
+            const feeOrders = [feeOrder];
+            const makerAssetFillAmount = orderWithFee.makerAssetAmount.dividedToIntegerBy(2);
+            const ethValue = orderWithFee.takerAssetAmount;
+
+            tx = await forwarderWrapper.marketBuyOrdersWithEthAsync(ordersWithFee, feeOrders, makerAssetFillAmount, {
+                value: ethValue,
                 from: takerAddress,
-                value: fillAmountWei,
-                gasPrice: DEFAULT_GAS_PRICE,
             });
+            const takerEthBalanceAfter = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
+            const forwarderEthBalance = await web3Wrapper.getBalanceInWeiAsync(forwarderContract.address);
             const newBalances = await erc20Wrapper.getBalancesAsync();
-            const takerTokenBalanceBefore = balancesBefore[takerAddress][zrxToken.address];
-            const takerTokenBalanceAfter = newBalances[takerAddress][zrxToken.address];
-            const takerWeiBalanceAfter = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
-            const expectedCostAfterGas = fillAmountWei.plus(tx.gasUsed);
-            expect(takerTokenBalanceAfter).to.be.bignumber.greaterThan(takerTokenBalanceBefore.plus(makerAssetAmount));
-            expect(takerWeiBalanceAfter).to.be.bignumber.equal(takerWeiBalanceBefore.minus(expectedCostAfterGas));
-        });
-        it('throws if fees are higher than 5% when buying zrx', async () => {
-            const highFeeZRXOrder = await orderFactory.newSignedOrderAsync({
-                makerAssetData: assetDataUtils.encodeERC20AssetData(zrxToken.address),
-                makerAssetAmount: signedOrder.makerAssetAmount,
-                takerFee: signedOrder.makerAssetAmount.times(0.06),
-            });
-            signedOrdersWithFee = [highFeeZRXOrder];
-            feeOrders = [];
-            const makerAssetAmount = signedOrder.makerAssetAmount.div(2);
-            const fillAmountWei = await forwarderWrapper.calculateMarketBuyFillAmountWeiAsync(
-                signedOrdersWithFee,
-                feeOrders,
-                feeProportion,
-                makerAssetAmount,
+
+            const primaryTakerAssetFillAmount = orderWithFee.takerAssetAmount.dividedToIntegerBy(2);
+            const feeAmount = orderWithFee.takerFee.dividedToIntegerBy(2);
+            const wethSpentOnFeeOrders = ForwarderWrapper.getWethForFeeOrders(feeAmount, feeOrders);
+            const totalEthSpent = primaryTakerAssetFillAmount
+                .plus(wethSpentOnFeeOrders)
+                .plus(gasPrice.times(tx.gasUsed));
+
+            expect(takerEthBalanceAfter).to.be.bignumber.equal(takerEthBalanceBefore.minus(totalEthSpent));
+            expect(newBalances[makerAddress][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][defaultMakerAssetAddress].minus(makerAssetFillAmount),
             );
-            return expectTransactionFailedAsync(
-                forwarderWrapper.marketBuyTokensWithEthAsync(signedOrdersWithFee, feeOrders, makerAssetAmount, {
-                    from: takerAddress,
-                    value: fillAmountWei,
-                }),
-                RevertReason.UnacceptableThreshold,
+            expect(newBalances[takerAddress][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                erc20Balances[takerAddress][defaultMakerAssetAddress].plus(makerAssetFillAmount),
             );
+            expect(newBalances[makerAddress][weth.address]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][weth.address].plus(primaryTakerAssetFillAmount).plus(wethSpentOnFeeOrders),
+            );
+            expect(newBalances[forwarderContract.address][weth.address]).to.be.bignumber.equal(constants.ZERO_AMOUNT);
+            expect(newBalances[forwarderContract.address][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                constants.ZERO_AMOUNT,
+            );
+            expect(forwarderEthBalance).to.be.bignumber.equal(constants.ZERO_AMOUNT);
         });
-        it('throws if fees are higher than 5% when buying erc20', async () => {
-            const highFeeERC20Order = await orderFactory.newSignedOrderAsync({
-                takerFee: signedOrder.makerAssetAmount.times(0.06),
+        it('should buy slightly greater than makerAssetAmount when buying ZRX', async () => {
+            orderWithFee = await orderFactory.newSignedOrderAsync({
+                makerAssetData: assetDataUtils.encodeERC20AssetData(zrxToken.address),
+                takerFee: Web3Wrapper.toBaseUnitAmount(new BigNumber(1), DECIMALS_DEFAULT),
             });
-            signedOrdersWithFee = [highFeeERC20Order];
-            feeOrders = [feeOrder];
-            const makerAssetAmount = signedOrder.makerAssetAmount.div(2);
-            const fillAmountWei = await forwarderWrapper.calculateMarketBuyFillAmountWeiAsync(
-                signedOrdersWithFee,
-                feeOrders,
-                feeProportion,
-                makerAssetAmount,
+            const ordersWithFee = [orderWithFee];
+            const feeOrders: SignedOrder[] = [];
+            const makerAssetFillAmount = orderWithFee.makerAssetAmount.dividedToIntegerBy(2);
+            const ethValue = orderWithFee.takerAssetAmount;
+            tx = await forwarderWrapper.marketBuyOrdersWithEthAsync(ordersWithFee, feeOrders, makerAssetFillAmount, {
+                value: ethValue,
+                from: takerAddress,
+            });
+            const takerEthBalanceAfter = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
+            const forwarderEthBalance = await web3Wrapper.getBalanceInWeiAsync(forwarderContract.address);
+            const newBalances = await erc20Wrapper.getBalancesAsync();
+
+            const primaryTakerAssetFillAmount = ForwarderWrapper.getWethForFeeOrders(
+                makerAssetFillAmount,
+                ordersWithFee,
             );
-            return expectTransactionFailedAsync(
-                forwarderWrapper.marketBuyTokensWithEthAsync(signedOrdersWithFee, feeOrders, makerAssetAmount, {
-                    from: takerAddress,
-                    value: fillAmountWei,
-                }),
-                RevertReason.UnacceptableThreshold as any,
+            const totalEthSpent = primaryTakerAssetFillAmount.plus(gasPrice.times(tx.gasUsed));
+            const makerAssetFilledAmount = orderWithFee.makerAssetAmount
+                .times(primaryTakerAssetFillAmount)
+                .dividedToIntegerBy(orderWithFee.takerAssetAmount);
+            const takerFeePaid = orderWithFee.takerFee
+                .times(primaryTakerAssetFillAmount)
+                .dividedToIntegerBy(orderWithFee.takerAssetAmount);
+            const makerFeePaid = orderWithFee.makerFee
+                .times(primaryTakerAssetFillAmount)
+                .dividedToIntegerBy(orderWithFee.takerAssetAmount);
+            const totalZrxPurchased = makerAssetFilledAmount.minus(takerFeePaid);
+            // Up to 1 wei worth of ZRX will be overbought per order
+            const maxOverboughtZrx = new BigNumber(1)
+                .times(orderWithFee.makerAssetAmount)
+                .dividedToIntegerBy(orderWithFee.takerAssetAmount);
+
+            expect(totalZrxPurchased).to.be.bignumber.gte(makerAssetFillAmount);
+            expect(totalZrxPurchased).to.be.bignumber.lte(makerAssetFillAmount.plus(maxOverboughtZrx));
+            expect(takerEthBalanceAfter).to.be.bignumber.equal(takerEthBalanceBefore.minus(totalEthSpent));
+            expect(newBalances[makerAddress][zrxToken.address]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][zrxToken.address].minus(makerAssetFilledAmount).minus(makerFeePaid),
             );
-        });
-        it('throws if makerAssetAmount is 0', async () => {
-            const makerAssetAmount = new BigNumber(0);
-            const fillAmountWei = await forwarderWrapper.calculateMarketBuyFillAmountWeiAsync(
-                signedOrdersWithFee,
-                feeOrders,
-                feeProportion,
-                makerAssetAmount,
+            expect(newBalances[takerAddress][zrxToken.address]).to.be.bignumber.equal(
+                erc20Balances[takerAddress][zrxToken.address].plus(totalZrxPurchased),
             );
-            return expectTransactionFailedAsync(
-                forwarderWrapper.marketBuyTokensWithEthAsync(signedOrdersWithFee, feeOrders, makerAssetAmount, {
-                    from: takerAddress,
-                    value: fillAmountWei,
-                }),
-                RevertReason.ValueGreaterThanZero as any,
+            expect(newBalances[makerAddress][weth.address]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][weth.address].plus(primaryTakerAssetFillAmount),
+            );
+            expect(newBalances[forwarderContract.address][weth.address]).to.be.bignumber.equal(constants.ZERO_AMOUNT);
+            expect(newBalances[forwarderContract.address][zrxToken.address]).to.be.bignumber.equal(
+                erc20Balances[forwarderContract.address][zrxToken.address],
             );
+            expect(forwarderEthBalance).to.be.bignumber.equal(constants.ZERO_AMOUNT);
         });
-        it('throws if the amount of ETH sent in is less than the takerAssetFilledAmount', async () => {
-            const makerAssetAmount = signedOrder.makerAssetAmount;
-            const fillAmount = signedOrder.takerAssetAmount.div(2);
-            const zero = new BigNumber(0);
-            // Deposit enough taker balance to fill the order
-            const wethDepositTxHash = await wethContract.deposit.sendTransactionAsync({
+        it('should not change balances if the amount of ETH sent is too low to fill the makerAssetAmount', async () => {
+            const ordersWithoutFee = [orderWithoutFee];
+            const feeOrders: SignedOrder[] = [];
+            const makerAssetFillAmount = orderWithoutFee.makerAssetAmount.dividedToIntegerBy(2);
+            const ethValue = orderWithoutFee.takerAssetAmount.dividedToIntegerBy(4);
+
+            tx = await forwarderWrapper.marketBuyOrdersWithEthAsync(ordersWithoutFee, feeOrders, makerAssetFillAmount, {
+                value: ethValue,
                 from: takerAddress,
-                value: signedOrder.takerAssetAmount,
             });
-            await web3Wrapper.awaitTransactionSuccessAsync(wethDepositTxHash);
-            // Transfer all of this WETH to the forwarding contract
-            const wethTransferTxHash = await wethContract.transfer.sendTransactionAsync(
-                forwarderContract.address,
-                signedOrder.takerAssetAmount,
-                { from: takerAddress },
-            );
-            await web3Wrapper.awaitTransactionSuccessAsync(wethTransferTxHash);
-            // We use the contract directly to get around wrapper validations and calculations
-            const formattedOrders = formatters.createMarketSellOrders(signedOrders, zero);
-            const formattedFeeOrders = formatters.createMarketSellOrders(feeOrders, zero);
-            return expectTransactionFailedAsync(
-                forwarderContract.marketBuyTokensWithEth.sendTransactionAsync(
-                    formattedOrders.orders,
-                    formattedOrders.signatures,
-                    formattedFeeOrders.orders,
-                    formattedFeeOrders.signatures,
-                    makerAssetAmount,
-                    zero,
-                    constants.NULL_ADDRESS,
-                    { value: fillAmount, from: takerAddress },
-                ),
-                RevertReason.InvalidMsgValue,
-            );
+            const takerEthBalanceAfter = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
+            const forwarderEthBalance = await web3Wrapper.getBalanceInWeiAsync(forwarderContract.address);
+            const newBalances = await erc20Wrapper.getBalancesAsync();
+
+            const totalEthSpent = gasPrice.times(tx.gasUsed);
+
+            expect(takerEthBalanceAfter).to.be.bignumber.equal(takerEthBalanceBefore.minus(totalEthSpent));
+            expect(newBalances).to.deep.equal(erc20Balances);
+            expect(forwarderEthBalance).to.be.bignumber.equal(constants.ZERO_AMOUNT);
         });
-    });
-    describe('marketBuyTokensWithEth - ERC721', async () => {
-        it('buys ERC721 assets', async () => {
+        it('should buy an ERC721 asset from a single order', async () => {
             const makerAssetId = erc721MakerAssetIds[0];
-            signedOrder = await orderFactory.newSignedOrderAsync({
+            orderWithoutFee = await orderFactory.newSignedOrderAsync({
                 makerAssetAmount: new BigNumber(1),
                 makerAssetData: assetDataUtils.encodeERC721AssetData(erc721Token.address, makerAssetId),
             });
-            feeOrders = [];
-            signedOrders = [signedOrder];
-            const makerAssetAmount = new BigNumber(signedOrders.length);
-            const fillAmountWei = await forwarderWrapper.calculateMarketBuyFillAmountWeiAsync(
-                signedOrders,
-                feeOrders,
-                feeProportion,
-                makerAssetAmount,
-            );
-            tx = await forwarderWrapper.marketBuyTokensWithEthAsync(signedOrders, feeOrders, makerAssetAmount, {
+            const ordersWithoutFee = [orderWithoutFee];
+            const feeOrders: SignedOrder[] = [];
+            const makerAssetFillAmount = new BigNumber(1);
+            const ethValue = orderWithFee.takerAssetAmount;
+
+            tx = await forwarderWrapper.marketBuyOrdersWithEthAsync(ordersWithoutFee, feeOrders, makerAssetFillAmount, {
                 from: takerAddress,
-                value: fillAmountWei,
+                value: ethValue,
             });
-            const newOwnerTakerAsset = await erc721Token.ownerOf.callAsync(makerAssetId);
-            expect(newOwnerTakerAsset).to.be.bignumber.equal(takerAddress);
+            const takerEthBalanceAfter = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
+            const forwarderEthBalance = await web3Wrapper.getBalanceInWeiAsync(forwarderContract.address);
+            const newOwner = await erc721Token.ownerOf.callAsync(makerAssetId);
+            const newBalances = await erc20Wrapper.getBalancesAsync();
+
+            const primaryTakerAssetFillAmount = ethValue;
+            const totalEthSpent = primaryTakerAssetFillAmount.plus(gasPrice.times(tx.gasUsed));
+            expect(newOwner).to.be.bignumber.equal(takerAddress);
+            expect(takerEthBalanceAfter).to.be.bignumber.equal(takerEthBalanceBefore.minus(totalEthSpent));
+            expect(newBalances[makerAddress][weth.address]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][weth.address].plus(primaryTakerAssetFillAmount),
+            );
+            expect(newBalances[forwarderContract.address][weth.address]).to.be.bignumber.equal(constants.ZERO_AMOUNT);
+            expect(newBalances[forwarderContract.address][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                constants.ZERO_AMOUNT,
+            );
+            expect(forwarderEthBalance).to.be.bignumber.equal(constants.ZERO_AMOUNT);
         });
-        it('buys ERC721 assets with fee abstraction', async () => {
+        it('should buy an ERC721 asset and ignore later orders with different makerAssetData', async () => {
             const makerAssetId = erc721MakerAssetIds[0];
-            signedOrder = await orderFactory.newSignedOrderAsync({
+            orderWithoutFee = await orderFactory.newSignedOrderAsync({
                 makerAssetAmount: new BigNumber(1),
-                takerFee: Web3Wrapper.toBaseUnitAmount(new BigNumber(1), DECIMALS_DEFAULT),
                 makerAssetData: assetDataUtils.encodeERC721AssetData(erc721Token.address, makerAssetId),
             });
-            signedOrders = [signedOrder];
-            const makerAssetAmount = new BigNumber(signedOrders.length);
-            const fillAmountWei = await forwarderWrapper.calculateMarketBuyFillAmountWeiAsync(
-                signedOrders,
-                feeOrders,
-                feeProportion,
-                makerAssetAmount,
-            );
-            tx = await forwarderWrapper.marketBuyTokensWithEthAsync(signedOrders, feeOrders, makerAssetAmount, {
+            const differentMakerAssetDataOrder = await orderFactory.newSignedOrderAsync();
+            const ordersWithoutFee = [orderWithoutFee, differentMakerAssetDataOrder];
+            const feeOrders: SignedOrder[] = [];
+            const makerAssetFillAmount = new BigNumber(1).plus(differentMakerAssetDataOrder.makerAssetAmount);
+            const ethValue = orderWithFee.takerAssetAmount;
+
+            tx = await forwarderWrapper.marketBuyOrdersWithEthAsync(ordersWithoutFee, feeOrders, makerAssetFillAmount, {
                 from: takerAddress,
-                value: fillAmountWei,
+                value: ethValue,
             });
-            const newOwnerTakerAsset = await erc721Token.ownerOf.callAsync(makerAssetId);
-            expect(newOwnerTakerAsset).to.be.bignumber.equal(takerAddress);
-        });
-        it('buys ERC721 assets with fee abstraction and pays fee to fee recipient', async () => {
-            const makerAssetId = erc721MakerAssetIds[0];
-            signedOrder = await orderFactory.newSignedOrderAsync({
-                makerAssetAmount: new BigNumber(1),
-                takerFee: Web3Wrapper.toBaseUnitAmount(new BigNumber(1), DECIMALS_DEFAULT),
-                makerAssetData: assetDataUtils.encodeERC721AssetData(erc721Token.address, makerAssetId),
-            });
-            signedOrders = [signedOrder];
-            feeProportion = 100;
-            const initTakerBalanceWei = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
-            const initFeeRecipientBalanceWei = await web3Wrapper.getBalanceInWeiAsync(feeRecipientAddress);
-            const makerAssetAmount = new BigNumber(signedOrders.length);
-            const fillAmountWei = await forwarderWrapper.calculateMarketBuyFillAmountWeiAsync(
-                signedOrders,
-                feeOrders,
-                feeProportion,
-                makerAssetAmount,
+            const takerEthBalanceAfter = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
+            const forwarderEthBalance = await web3Wrapper.getBalanceInWeiAsync(forwarderContract.address);
+            const newOwner = await erc721Token.ownerOf.callAsync(makerAssetId);
+            const newBalances = await erc20Wrapper.getBalancesAsync();
+
+            const primaryTakerAssetFillAmount = ethValue;
+            const totalEthSpent = primaryTakerAssetFillAmount.plus(gasPrice.times(tx.gasUsed));
+            expect(newOwner).to.be.bignumber.equal(takerAddress);
+            expect(takerEthBalanceAfter).to.be.bignumber.equal(takerEthBalanceBefore.minus(totalEthSpent));
+            expect(newBalances[makerAddress][weth.address]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][weth.address].plus(primaryTakerAssetFillAmount),
             );
-            tx = await forwarderWrapper.marketBuyTokensWithEthAsync(
-                signedOrders,
-                feeOrders,
-                makerAssetAmount,
-                {
-                    from: takerAddress,
-                    value: fillAmountWei,
-                    gasPrice: DEFAULT_GAS_PRICE,
-                },
-                {
-                    feeProportion,
-                    feeRecipient: feeRecipientAddress,
-                },
+            expect(newBalances[forwarderContract.address][weth.address]).to.be.bignumber.equal(constants.ZERO_AMOUNT);
+            expect(newBalances[forwarderContract.address][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                constants.ZERO_AMOUNT,
             );
-            const afterFeeRecipientEthBalance = await web3Wrapper.getBalanceInWeiAsync(feeRecipientAddress);
-            const afterTakerBalanceWei = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
-            const takerFilledAmount = initTakerBalanceWei.minus(afterTakerBalanceWei).plus(tx.gasUsed);
-            const newOwnerTakerAsset = await erc721Token.ownerOf.callAsync(makerAssetId);
-            expect(newOwnerTakerAsset).to.be.bignumber.equal(takerAddress);
-            const balanceDiff = afterFeeRecipientEthBalance.minus(initFeeRecipientBalanceWei);
-            expect(takerFilledAmount.dividedToIntegerBy(balanceDiff)).to.be.bignumber.equal(101);
-            expect(takerFilledAmount.minus(balanceDiff).dividedToIntegerBy(balanceDiff)).to.be.bignumber.equal(100);
-        });
-        it('buys multiple ERC721 assets with fee abstraction and pays fee to fee recipient', async () => {
-            const makerAssetId1 = erc721MakerAssetIds[0];
-            const makerAssetId2 = erc721MakerAssetIds[1];
-            const signedOrder1 = await orderFactory.newSignedOrderAsync({
-                makerAssetAmount: new BigNumber(1),
-                takerFee: Web3Wrapper.toBaseUnitAmount(new BigNumber(3), DECIMALS_DEFAULT),
-                makerAssetData: assetDataUtils.encodeERC721AssetData(erc721Token.address, makerAssetId1),
-            });
-            const signedOrder2 = await orderFactory.newSignedOrderAsync({
-                makerAssetAmount: new BigNumber(1),
-                takerFee: Web3Wrapper.toBaseUnitAmount(new BigNumber(4), DECIMALS_DEFAULT),
-                makerAssetData: assetDataUtils.encodeERC721AssetData(erc721Token.address, makerAssetId2),
-            });
-            signedOrders = [signedOrder1, signedOrder2];
-            feeProportion = 10;
-            const makerAssetAmount = new BigNumber(signedOrders.length);
-            const fillAmountWei = await forwarderWrapper.calculateMarketBuyFillAmountWeiAsync(
-                signedOrders,
-                feeOrders,
-                feeProportion,
-                makerAssetAmount,
+            expect(forwarderEthBalance).to.be.bignumber.equal(constants.ZERO_AMOUNT);
+            expect(newBalances[makerAddress][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][defaultMakerAssetAddress],
+            );
+            expect(newBalances[takerAddress][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                erc20Balances[takerAddress][defaultMakerAssetAddress],
             );
-            tx = await forwarderWrapper.marketBuyTokensWithEthAsync(signedOrders, feeOrders, makerAssetAmount, {
-                from: takerAddress,
-                value: fillAmountWei,
-            });
-            const newOwnerTakerAsset1 = await erc721Token.ownerOf.callAsync(makerAssetId1);
-            expect(newOwnerTakerAsset1).to.be.bignumber.equal(takerAddress);
-            const newOwnerTakerAsset2 = await erc721Token.ownerOf.callAsync(makerAssetId2);
-            expect(newOwnerTakerAsset2).to.be.bignumber.equal(takerAddress);
         });
-        it('buys ERC721 assets with fee abstraction and handles fee orders filled and excess eth', async () => {
+        it('should buy an ERC721 asset and pay ZRX fees from a single fee order', async () => {
             const makerAssetId = erc721MakerAssetIds[0];
-            feeProportion = 0;
-            // In this scenario a total of 6 ZRX fees need to be paid.
-            // There are two fee orders, but the first fee order is partially filled while
-            // the Forwarding contract tx is in the mempool.
-            const erc721MakerAssetAmount = new BigNumber(1);
-            signedOrder = await orderFactory.newSignedOrderAsync({
-                makerAssetAmount: erc721MakerAssetAmount,
-                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), DECIMALS_DEFAULT),
-                takerFee: Web3Wrapper.toBaseUnitAmount(new BigNumber(6), DECIMALS_DEFAULT),
+            orderWithFee = await orderFactory.newSignedOrderAsync({
+                makerAssetAmount: new BigNumber(1),
                 makerAssetData: assetDataUtils.encodeERC721AssetData(erc721Token.address, makerAssetId),
+                takerFee: Web3Wrapper.toBaseUnitAmount(new BigNumber(1), DECIMALS_DEFAULT),
             });
-            signedOrders = [signedOrder];
-            const firstFeeOrder = await orderFactory.newSignedOrderAsync({
-                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(8), DECIMALS_DEFAULT),
-                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(0.1), DECIMALS_DEFAULT),
-                makerAssetData: assetDataUtils.encodeERC20AssetData(zrxToken.address),
-                takerFee: Web3Wrapper.toBaseUnitAmount(new BigNumber(0), DECIMALS_DEFAULT),
-            });
-            const secondFeeOrder = await orderFactory.newSignedOrderAsync({
-                makerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(8), DECIMALS_DEFAULT),
-                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(0.12), DECIMALS_DEFAULT),
-                makerAssetData: assetDataUtils.encodeERC20AssetData(zrxToken.address),
-                takerFee: Web3Wrapper.toBaseUnitAmount(new BigNumber(0), DECIMALS_DEFAULT),
-            });
-            feeOrders = [firstFeeOrder, secondFeeOrder];
-            const makerAssetAmount = new BigNumber(signedOrders.length);
-            const fillAmountWei = await forwarderWrapper.calculateMarketBuyFillAmountWeiAsync(
-                signedOrders,
-                feeOrders,
-                feeProportion,
-                erc721MakerAssetAmount,
-            );
-            // Simulate another otherAddress user partially filling firstFeeOrder
-            const firstFeeOrderFillAmount = firstFeeOrder.makerAssetAmount.div(2);
-            tx = await forwarderWrapper.marketBuyTokensWithEthAsync([firstFeeOrder], [], firstFeeOrderFillAmount, {
-                from: otherAddress,
-                value: fillAmountWei,
-            });
-            // For tests we calculate how much this should've cost given that firstFeeOrder was filled
-            const expectedFillAmountWei = await forwarderWrapper.calculateMarketBuyFillAmountWeiAsync(
-                signedOrders,
-                feeOrders,
-                feeProportion,
-                erc721MakerAssetAmount,
-            );
-            // With 4 ZRX remaining in firstFeeOrder, the secondFeeOrder will need to be filled to make up
-            // the total amount of fees required (6)
-            // Since the fee orders can be filled while the transaction is pending the user safely sends in
-            // extra ether to cover any slippage
-            const initEthBalance = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
-            const slippageFillAmountWei = fillAmountWei.times(2);
-            tx = await forwarderWrapper.marketBuyTokensWithEthAsync(signedOrders, feeOrders, makerAssetAmount, {
+            const ordersWithFee = [orderWithFee];
+            const feeOrders = [feeOrder];
+            const makerAssetFillAmount = orderWithFee.makerAssetAmount;
+            const primaryTakerAssetFillAmount = orderWithFee.takerAssetAmount;
+            const feeAmount = orderWithFee.takerFee;
+            const wethSpentOnFeeOrders = ForwarderWrapper.getWethForFeeOrders(feeAmount, feeOrders);
+            const ethValue = primaryTakerAssetFillAmount.plus(wethSpentOnFeeOrders);
+
+            tx = await forwarderWrapper.marketBuyOrdersWithEthAsync(ordersWithFee, feeOrders, makerAssetFillAmount, {
+                value: ethValue,
                 from: takerAddress,
-                value: slippageFillAmountWei,
-                gasPrice: DEFAULT_GAS_PRICE,
             });
-            const afterEthBalance = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
-            const expectedEthBalanceAfterGasCosts = initEthBalance.minus(expectedFillAmountWei).minus(tx.gasUsed);
-            const newOwnerTakerAsset = await erc721Token.ownerOf.callAsync(makerAssetId);
-            expect(newOwnerTakerAsset).to.be.bignumber.equal(takerAddress);
-            expect(afterEthBalance).to.be.bignumber.equal(expectedEthBalanceAfterGasCosts);
+            const takerEthBalanceAfter = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
+            const forwarderEthBalance = await web3Wrapper.getBalanceInWeiAsync(forwarderContract.address);
+            const newOwner = await erc721Token.ownerOf.callAsync(makerAssetId);
+            const newBalances = await erc20Wrapper.getBalancesAsync();
+
+            const totalEthSpent = ethValue.plus(gasPrice.times(tx.gasUsed));
+
+            expect(newOwner).to.be.bignumber.equal(takerAddress);
+            expect(takerEthBalanceAfter).to.be.bignumber.equal(takerEthBalanceBefore.minus(totalEthSpent));
+            expect(newBalances[makerAddress][weth.address]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][weth.address].plus(primaryTakerAssetFillAmount).plus(wethSpentOnFeeOrders),
+            );
+            expect(newBalances[forwarderContract.address][weth.address]).to.be.bignumber.equal(constants.ZERO_AMOUNT);
+            expect(newBalances[forwarderContract.address][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                constants.ZERO_AMOUNT,
+            );
+            expect(forwarderEthBalance).to.be.bignumber.equal(constants.ZERO_AMOUNT);
         });
-        it('buys ERC721 assets with fee abstraction and handles fee orders filled', async () => {
+        it('should buy an ERC721 asset and pay ZRX fees from multiple fee orders', async () => {
             const makerAssetId = erc721MakerAssetIds[0];
-            feeProportion = 0;
-            // In this scenario a total of 6 ZRX fees need to be paid.
-            // There are two fee orders, but the first fee order is partially filled while
-            // the Forwarding contract tx is in the mempool.
-            const erc721MakerAssetAmount = new BigNumber(1);
-            signedOrder = await orderFactory.newSignedOrderAsync({
-                makerAssetAmount: erc721MakerAssetAmount,
-                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(10), DECIMALS_DEFAULT),
-                takerFee: Web3Wrapper.toBaseUnitAmount(new BigNumber(6), DECIMALS_DEFAULT),
+            orderWithFee = await orderFactory.newSignedOrderAsync({
+                makerAssetAmount: new BigNumber(1),
                 makerAssetData: assetDataUtils.encodeERC721AssetData(erc721Token.address, makerAssetId),
+                takerFee: Web3Wrapper.toBaseUnitAmount(new BigNumber(1), DECIMALS_DEFAULT),
             });
-            const zrxMakerAssetAmount = Web3Wrapper.toBaseUnitAmount(new BigNumber(8), DECIMALS_DEFAULT);
-            signedOrders = [signedOrder];
+            const ordersWithFee = [orderWithFee];
+            const makerAssetData = assetDataUtils.encodeERC20AssetData(zrxToken.address);
+            const makerAssetAmount = orderWithFee.takerFee.dividedToIntegerBy(2);
+            const takerAssetAmount = feeOrder.takerAssetAmount
+                .times(makerAssetAmount)
+                .dividedToIntegerBy(feeOrder.makerAssetAmount);
+
             const firstFeeOrder = await orderFactory.newSignedOrderAsync({
-                makerAssetAmount: zrxMakerAssetAmount,
-                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(0.1), DECIMALS_DEFAULT),
-                makerAssetData: assetDataUtils.encodeERC20AssetData(zrxToken.address),
-                takerFee: Web3Wrapper.toBaseUnitAmount(new BigNumber(0), DECIMALS_DEFAULT),
+                makerAssetData,
+                makerAssetAmount,
+                takerAssetAmount,
             });
             const secondFeeOrder = await orderFactory.newSignedOrderAsync({
-                makerAssetAmount: zrxMakerAssetAmount,
-                takerAssetAmount: Web3Wrapper.toBaseUnitAmount(new BigNumber(0.12), DECIMALS_DEFAULT),
-                makerAssetData: assetDataUtils.encodeERC20AssetData(zrxToken.address),
-                takerFee: Web3Wrapper.toBaseUnitAmount(new BigNumber(0), DECIMALS_DEFAULT),
-            });
-            feeOrders = [firstFeeOrder, secondFeeOrder];
-            const makerAssetAmount = new BigNumber(signedOrders.length);
-            const fillAmountWei = await forwarderWrapper.calculateMarketBuyFillAmountWeiAsync(
-                signedOrders,
-                feeOrders,
-                feeProportion,
-                erc721MakerAssetAmount,
-            );
-            // Simulate another otherAddress user partially filling firstFeeOrder
-            const firstFeeOrderFillAmount = firstFeeOrder.makerAssetAmount.div(2);
-            tx = await forwarderWrapper.marketBuyTokensWithEthAsync([firstFeeOrder], [], firstFeeOrderFillAmount, {
-                from: otherAddress,
-                value: fillAmountWei,
+                makerAssetData,
+                makerAssetAmount,
+                takerAssetAmount,
             });
-            const expectedFillAmountWei = await forwarderWrapper.calculateMarketBuyFillAmountWeiAsync(
-                signedOrders,
-                feeOrders,
-                feeProportion,
-                erc721MakerAssetAmount,
-            );
-            tx = await forwarderWrapper.marketBuyTokensWithEthAsync(signedOrders, feeOrders, makerAssetAmount, {
+            const feeOrders = [firstFeeOrder, secondFeeOrder];
+
+            const makerAssetFillAmount = orderWithFee.makerAssetAmount;
+            const primaryTakerAssetFillAmount = orderWithFee.takerAssetAmount;
+            const feeAmount = orderWithFee.takerFee;
+            const wethSpentOnFeeOrders = ForwarderWrapper.getWethForFeeOrders(feeAmount, feeOrders);
+            const ethValue = primaryTakerAssetFillAmount.plus(wethSpentOnFeeOrders);
+
+            tx = await forwarderWrapper.marketBuyOrdersWithEthAsync(ordersWithFee, feeOrders, makerAssetFillAmount, {
+                value: ethValue,
                 from: takerAddress,
-                value: expectedFillAmountWei,
             });
-            const newOwnerTakerAsset = await erc721Token.ownerOf.callAsync(makerAssetId);
-            expect(newOwnerTakerAsset).to.be.bignumber.equal(takerAddress);
+            const takerEthBalanceAfter = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
+            const forwarderEthBalance = await web3Wrapper.getBalanceInWeiAsync(forwarderContract.address);
+            const newOwner = await erc721Token.ownerOf.callAsync(makerAssetId);
+            const newBalances = await erc20Wrapper.getBalancesAsync();
+
+            const totalEthSpent = ethValue.plus(gasPrice.times(tx.gasUsed));
+
+            expect(newOwner).to.be.bignumber.equal(takerAddress);
+            expect(takerEthBalanceAfter).to.be.bignumber.equal(takerEthBalanceBefore.minus(totalEthSpent));
+            expect(newBalances[makerAddress][weth.address]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][weth.address].plus(primaryTakerAssetFillAmount).plus(wethSpentOnFeeOrders),
+            );
+            expect(newBalances[forwarderContract.address][weth.address]).to.be.bignumber.equal(constants.ZERO_AMOUNT);
+            expect(newBalances[forwarderContract.address][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                constants.ZERO_AMOUNT,
+            );
+            expect(forwarderEthBalance).to.be.bignumber.equal(constants.ZERO_AMOUNT);
         });
-        it('throws when mixed ERC721 and ERC20 assets', async () => {
-            const makerAssetId = erc721MakerAssetIds[0];
-            const erc721SignedOrder = await orderFactory.newSignedOrderAsync({
-                makerAssetAmount: new BigNumber(1),
-                makerAssetData: assetDataUtils.encodeERC721AssetData(erc721Token.address, makerAssetId),
-            });
-            const erc20SignedOrder = await orderFactory.newSignedOrderAsync();
-            signedOrders = [erc721SignedOrder, erc20SignedOrder];
-            const makerAssetAmount = new BigNumber(signedOrders.length);
-            const fillAmountWei = erc20SignedOrder.takerAssetAmount.plus(erc721SignedOrder.takerAssetAmount);
-            return expectTransactionFailedAsync(
-                forwarderWrapper.marketBuyTokensWithEthAsync(signedOrders, feeOrders, makerAssetAmount, {
+    });
+    describe('marketBuyOrdersWithEth with extra fees', () => {
+        it('should buy an asset and send fee to feeRecipient', async () => {
+            const ordersWithoutFee = [orderWithoutFee];
+            const feeOrders: SignedOrder[] = [];
+            const makerAssetFillAmount = orderWithoutFee.makerAssetAmount.dividedToIntegerBy(2);
+            const ethValue = orderWithoutFee.takerAssetAmount;
+
+            const baseFeePercentage = 2;
+            feePercentage = ForwarderWrapper.getPercentageOfValue(constants.PERCENTAGE_DENOMINATOR, baseFeePercentage);
+            const feeRecipientEthBalanceBefore = await web3Wrapper.getBalanceInWeiAsync(feeRecipientAddress);
+            tx = await forwarderWrapper.marketBuyOrdersWithEthAsync(
+                ordersWithoutFee,
+                feeOrders,
+                makerAssetFillAmount,
+                {
+                    value: ethValue,
                     from: takerAddress,
-                    value: fillAmountWei,
-                }),
-                RevertReason.LibBytesGreaterOrEqualTo32LengthRequired,
+                },
+                { feePercentage, feeRecipient: feeRecipientAddress },
             );
+            const takerEthBalanceAfter = await web3Wrapper.getBalanceInWeiAsync(takerAddress);
+            const forwarderEthBalance = await web3Wrapper.getBalanceInWeiAsync(forwarderContract.address);
+            const feeRecipientEthBalanceAfter = await web3Wrapper.getBalanceInWeiAsync(feeRecipientAddress);
+            const newBalances = await erc20Wrapper.getBalancesAsync();
+
+            const primaryTakerAssetFillAmount = orderWithoutFee.takerAssetAmount.dividedToIntegerBy(2);
+            const ethSpentOnFee = ForwarderWrapper.getPercentageOfValue(primaryTakerAssetFillAmount, baseFeePercentage);
+            const totalEthSpent = primaryTakerAssetFillAmount.plus(ethSpentOnFee).plus(gasPrice.times(tx.gasUsed));
+
+            expect(feeRecipientEthBalanceAfter).to.be.bignumber.equal(feeRecipientEthBalanceBefore.plus(ethSpentOnFee));
+            expect(takerEthBalanceAfter).to.be.bignumber.equal(takerEthBalanceBefore.minus(totalEthSpent));
+            expect(newBalances[makerAddress][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][defaultMakerAssetAddress].minus(makerAssetFillAmount),
+            );
+            expect(newBalances[takerAddress][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                erc20Balances[takerAddress][defaultMakerAssetAddress].plus(makerAssetFillAmount),
+            );
+            expect(newBalances[makerAddress][weth.address]).to.be.bignumber.equal(
+                erc20Balances[makerAddress][weth.address].plus(primaryTakerAssetFillAmount),
+            );
+            expect(newBalances[forwarderContract.address][weth.address]).to.be.bignumber.equal(constants.ZERO_AMOUNT);
+            expect(newBalances[forwarderContract.address][defaultMakerAssetAddress]).to.be.bignumber.equal(
+                constants.ZERO_AMOUNT,
+            );
+            expect(forwarderEthBalance).to.be.bignumber.equal(constants.ZERO_AMOUNT);
         });
-        it('throws when mixed ERC721 and ERC20 assets with ERC20 first', async () => {
-            const makerAssetId = erc721MakerAssetIds[0];
-            const erc721SignedOrder = await orderFactory.newSignedOrderAsync({
-                makerAssetAmount: new BigNumber(1),
-                makerAssetData: assetDataUtils.encodeERC721AssetData(erc721Token.address, makerAssetId),
-            });
-            const erc20SignedOrder = await orderFactory.newSignedOrderAsync();
-            signedOrders = [erc20SignedOrder, erc721SignedOrder];
-            const makerAssetAmount = new BigNumber(signedOrders.length);
-            const fillAmountWei = erc20SignedOrder.takerAssetAmount.plus(erc721SignedOrder.takerAssetAmount);
-            return expectTransactionFailedAsync(
-                forwarderWrapper.marketBuyTokensWithEthAsync(signedOrders, feeOrders, makerAssetAmount, {
-                    from: takerAddress,
-                    value: fillAmountWei,
-                }),
-                RevertReason.InvalidTakerAmount,
+        it('should fail if the fee is set too high', async () => {
+            const ordersWithoutFee = [orderWithoutFee];
+            const feeOrders: SignedOrder[] = [];
+            const makerAssetFillAmount = orderWithoutFee.makerAssetAmount.dividedToIntegerBy(2);
+            const ethValue = orderWithoutFee.takerAssetAmount;
+
+            const baseFeePercentage = 6;
+            feePercentage = ForwarderWrapper.getPercentageOfValue(constants.PERCENTAGE_DENOMINATOR, baseFeePercentage);
+            await expectTransactionFailedAsync(
+                forwarderWrapper.marketBuyOrdersWithEthAsync(
+                    ordersWithoutFee,
+                    feeOrders,
+                    makerAssetFillAmount,
+                    {
+                        value: ethValue,
+                        from: takerAddress,
+                    },
+                    { feePercentage, feeRecipient: feeRecipientAddress },
+                ),
+                RevertReason.FeePercentageTooLarge,
+            );
+        });
+        it('should fail if there is not enough ETH remaining to pay the fee', async () => {
+            const ordersWithoutFee = [orderWithoutFee];
+            const feeOrders: SignedOrder[] = [];
+            const makerAssetFillAmount = orderWithoutFee.makerAssetAmount.dividedToIntegerBy(2);
+            const ethValue = orderWithoutFee.takerAssetAmount.dividedToIntegerBy(2);
+
+            const baseFeePercentage = 2;
+            feePercentage = ForwarderWrapper.getPercentageOfValue(constants.PERCENTAGE_DENOMINATOR, baseFeePercentage);
+            await expectTransactionFailedAsync(
+                forwarderWrapper.marketBuyOrdersWithEthAsync(
+                    ordersWithoutFee,
+                    feeOrders,
+                    makerAssetFillAmount,
+                    {
+                        value: ethValue,
+                        from: takerAddress,
+                    },
+                    { feePercentage, feeRecipient: feeRecipientAddress },
+                ),
+                RevertReason.InsufficientEthRemaining,
             );
         });
     });
diff --git a/packages/contracts/test/utils/constants.ts b/packages/contracts/test/utils/constants.ts
index 7dac38f56..65eaee398 100644
--- a/packages/contracts/test/utils/constants.ts
+++ b/packages/contracts/test/utils/constants.ts
@@ -49,4 +49,6 @@ export const constants = {
         takerFee: Web3Wrapper.toBaseUnitAmount(new BigNumber(1), 18),
     },
     WORD_LENGTH: 32,
+    ZERO_AMOUNT: new BigNumber(0),
+    PERCENTAGE_DENOMINATOR: new BigNumber(10).pow(18),
 };
diff --git a/packages/contracts/test/utils/forwarder_wrapper.ts b/packages/contracts/test/utils/forwarder_wrapper.ts
index e39df14b1..ef7476e36 100644
--- a/packages/contracts/test/utils/forwarder_wrapper.ts
+++ b/packages/contracts/test/utils/forwarder_wrapper.ts
@@ -1,5 +1,4 @@
-import { assetDataUtils } from '@0xproject/order-utils';
-import { AssetProxyId, SignedOrder } from '@0xproject/types';
+import { SignedOrder } from '@0xproject/types';
 import { BigNumber } from '@0xproject/utils';
 import { Web3Wrapper } from '@0xproject/web3-wrapper';
 import { Provider, TransactionReceiptWithDecodedLogs, TxDataPayable } from 'ethereum-types';
@@ -12,209 +11,108 @@ import { formatters } from './formatters';
 import { LogDecoder } from './log_decoder';
 import { MarketSellOrders } from './types';
 
-const DEFAULT_FEE_PROPORTION = 0;
-const PERCENTAGE_DENOMINATOR = 10000;
-const ZERO_AMOUNT = new BigNumber(0);
-const INSUFFICENT_ORDERS_FOR_MAKER_AMOUNT = 'Unable to satisfy makerAssetFillAmount with provided orders';
-
 export class ForwarderWrapper {
     private readonly _web3Wrapper: Web3Wrapper;
     private readonly _forwarderContract: ForwarderContract;
     private readonly _logDecoder: LogDecoder;
-    private readonly _zrxAddress: string;
-    private static _createOptimizedSellOrders(signedOrders: SignedOrder[]): MarketSellOrders {
-        const marketSellOrders = formatters.createMarketSellOrders(signedOrders, ZERO_AMOUNT);
-        const assetDataId = assetDataUtils.decodeAssetProxyId(signedOrders[0].makerAssetData);
-        // Contract will fill this in for us as all of the assetData is assumed to be the same
-        for (let i = 0; i < signedOrders.length; i++) {
-            if (i !== 0 && assetDataId === AssetProxyId.ERC20) {
-                // Forwarding contract will fill this in from the first order
-                marketSellOrders.orders[i].makerAssetData = constants.NULL_BYTES;
+    public static getPercentageOfValue(value: BigNumber, percentage: number): BigNumber {
+        const numerator = constants.PERCENTAGE_DENOMINATOR.times(percentage).dividedToIntegerBy(100);
+        const newValue = value.times(numerator).dividedToIntegerBy(constants.PERCENTAGE_DENOMINATOR);
+        return newValue;
+    }
+    public static getWethForFeeOrders(feeAmount: BigNumber, feeOrders: SignedOrder[]): BigNumber {
+        let wethAmount = new BigNumber(0);
+        let remainingFeeAmount = feeAmount;
+        _.forEach(feeOrders, feeOrder => {
+            const feeAvailable = feeOrder.makerAssetAmount.minus(feeOrder.takerFee);
+            if (!remainingFeeAmount.isZero() && feeAvailable.gt(remainingFeeAmount)) {
+                wethAmount = wethAmount
+                    .plus(feeOrder.takerAssetAmount.times(remainingFeeAmount).dividedToIntegerBy(feeAvailable))
+                    .plus(1);
+                remainingFeeAmount = new BigNumber(0);
+            } else if (!remainingFeeAmount.isZero()) {
+                wethAmount = wethAmount.plus(feeOrder.takerAssetAmount);
+                remainingFeeAmount = remainingFeeAmount.minus(feeAvailable);
             }
-            marketSellOrders.orders[i].takerAssetData = constants.NULL_BYTES;
-        }
-        return marketSellOrders;
+        });
+        return wethAmount;
     }
-    private static _createOptimizedZRXSellOrders(signedOrders: SignedOrder[]): MarketSellOrders {
-        const marketSellOrders = formatters.createMarketSellOrders(signedOrders, ZERO_AMOUNT);
-        // Contract will fill this in for us as all of the assetData is assumed to be the same
-        for (let i = 0; i < signedOrders.length; i++) {
-            marketSellOrders.orders[i].makerAssetData = constants.NULL_BYTES;
-            marketSellOrders.orders[i].takerAssetData = constants.NULL_BYTES;
-        }
-        return marketSellOrders;
+    private static _createOptimizedOrders(signedOrders: SignedOrder[]): MarketSellOrders {
+        _.forEach(signedOrders, (signedOrder, index) => {
+            signedOrder.takerAssetData = constants.NULL_BYTES;
+            if (index > 0) {
+                signedOrder.makerAssetData = constants.NULL_BYTES;
+            }
+        });
+        const params = formatters.createMarketSellOrders(signedOrders, constants.ZERO_AMOUNT);
+        return params;
     }
-    private static _calculateAdditionalFeeProportionAmount(feeProportion: number, fillAmountWei: BigNumber): BigNumber {
-        if (feeProportion > 0) {
-            // Add to the total ETH transaction to ensure all NFTs can be filled after fees
-            // 150 = 1.5% = 0.015
-            const denominator = new BigNumber(1).minus(new BigNumber(feeProportion).dividedBy(PERCENTAGE_DENOMINATOR));
-            return fillAmountWei.dividedBy(denominator).round(0, BigNumber.ROUND_FLOOR);
-        }
-        return fillAmountWei;
+    private static _createOptimizedZrxOrders(signedOrders: SignedOrder[]): MarketSellOrders {
+        _.forEach(signedOrders, signedOrder => {
+            signedOrder.makerAssetData = constants.NULL_BYTES;
+            signedOrder.takerAssetData = constants.NULL_BYTES;
+        });
+        const params = formatters.createMarketSellOrders(signedOrders, constants.ZERO_AMOUNT);
+        return params;
     }
-    constructor(contractInstance: ForwarderContract, provider: Provider, zrxAddress: string) {
+    constructor(contractInstance: ForwarderContract, provider: Provider) {
         this._forwarderContract = contractInstance;
         this._web3Wrapper = new Web3Wrapper(provider);
         this._logDecoder = new LogDecoder(this._web3Wrapper, this._forwarderContract.address);
-        // this._web3Wrapper.abiDecoder.addABI(contractInstance.abi);
-        this._zrxAddress = zrxAddress;
     }
-    public async marketBuyTokensWithEthAsync(
+    public async marketSellOrdersWithEthAsync(
         orders: SignedOrder[],
         feeOrders: SignedOrder[],
-        makerTokenBuyAmount: BigNumber,
         txData: TxDataPayable,
-        opts: { feeProportion?: number; feeRecipient?: string } = {},
+        opts: { feePercentage?: BigNumber; feeRecipient?: string } = {},
     ): Promise<TransactionReceiptWithDecodedLogs> {
-        const params = ForwarderWrapper._createOptimizedSellOrders(orders);
-        const feeParams = ForwarderWrapper._createOptimizedZRXSellOrders(feeOrders);
-        const feeProportion = _.isUndefined(opts.feeProportion) ? DEFAULT_FEE_PROPORTION : opts.feeProportion;
+        const params = ForwarderWrapper._createOptimizedOrders(orders);
+        const feeParams = ForwarderWrapper._createOptimizedZrxOrders(feeOrders);
+        const feePercentage = _.isUndefined(opts.feePercentage) ? constants.ZERO_AMOUNT : opts.feePercentage;
         const feeRecipient = _.isUndefined(opts.feeRecipient) ? constants.NULL_ADDRESS : opts.feeRecipient;
-        const txHash: string = await this._forwarderContract.marketBuyTokensWithEth.sendTransactionAsync(
+        const txHash = await this._forwarderContract.marketSellOrdersWithEth.sendTransactionAsync(
             params.orders,
             params.signatures,
             feeParams.orders,
             feeParams.signatures,
-            makerTokenBuyAmount,
-            feeProportion,
+            feePercentage,
             feeRecipient,
             txData,
         );
         const tx = await this._logDecoder.getTxWithDecodedLogsAsync(txHash);
         return tx;
     }
-    public async marketSellEthForERC20Async(
+    public async marketBuyOrdersWithEthAsync(
         orders: SignedOrder[],
         feeOrders: SignedOrder[],
+        makerAssetFillAmount: BigNumber,
         txData: TxDataPayable,
-        opts: { feeProportion?: number; feeRecipient?: string } = {},
+        opts: { feePercentage?: BigNumber; feeRecipient?: string } = {},
     ): Promise<TransactionReceiptWithDecodedLogs> {
-        const assetDataId = assetDataUtils.decodeAssetProxyId(orders[0].makerAssetData);
-        if (assetDataId !== AssetProxyId.ERC20) {
-            throw new Error('Asset type not supported by marketSellEthForERC20');
-        }
-        const params = ForwarderWrapper._createOptimizedSellOrders(orders);
-        const feeParams = ForwarderWrapper._createOptimizedZRXSellOrders(feeOrders);
-        const feeProportion = _.isUndefined(opts.feeProportion) ? DEFAULT_FEE_PROPORTION : opts.feeProportion;
+        const params = ForwarderWrapper._createOptimizedOrders(orders);
+        const feeParams = ForwarderWrapper._createOptimizedZrxOrders(feeOrders);
+        const feePercentage = _.isUndefined(opts.feePercentage) ? constants.ZERO_AMOUNT : opts.feePercentage;
         const feeRecipient = _.isUndefined(opts.feeRecipient) ? constants.NULL_ADDRESS : opts.feeRecipient;
-        const txHash: string = await this._forwarderContract.marketSellEthForERC20.sendTransactionAsync(
+        const txHash = await this._forwarderContract.marketBuyOrdersWithEth.sendTransactionAsync(
             params.orders,
+            makerAssetFillAmount,
             params.signatures,
             feeParams.orders,
             feeParams.signatures,
-            feeProportion,
+            feePercentage,
             feeRecipient,
             txData,
         );
         const tx = await this._logDecoder.getTxWithDecodedLogsAsync(txHash);
         return tx;
     }
-    public async calculateMarketBuyFillAmountWeiAsync(
-        orders: SignedOrder[],
-        feeOrders: SignedOrder[],
-        feeProportion: number,
-        makerAssetFillAmount: BigNumber,
-    ): Promise<BigNumber> {
-        const assetProxyId = assetDataUtils.decodeAssetProxyId(orders[0].makerAssetData);
-        switch (assetProxyId) {
-            case AssetProxyId.ERC20: {
-                const fillAmountWei = this._calculateMarketBuyERC20FillAmountAsync(
-                    orders,
-                    feeOrders,
-                    feeProportion,
-                    makerAssetFillAmount,
-                );
-                return fillAmountWei;
-            }
-            case AssetProxyId.ERC721: {
-                const fillAmountWei = await this._calculateMarketBuyERC721FillAmountAsync(
-                    orders,
-                    feeOrders,
-                    feeProportion,
-                );
-                return fillAmountWei;
-            }
-            default:
-                throw new Error(`Invalid Asset Proxy Id: ${assetProxyId}`);
-        }
-    }
-    private async _calculateMarketBuyERC20FillAmountAsync(
-        orders: SignedOrder[],
-        feeOrders: SignedOrder[],
-        feeProportion: number,
-        makerAssetFillAmount: BigNumber,
-    ): Promise<BigNumber> {
-        const makerAssetData = assetDataUtils.decodeAssetDataOrThrow(orders[0].makerAssetData);
-        const makerAssetToken = makerAssetData.tokenAddress;
-        const params = formatters.createMarketBuyOrders(orders, makerAssetFillAmount);
-
-        let fillAmountWei;
-        if (makerAssetToken === this._zrxAddress) {
-            // If buying ZRX we buy the tokens and fees from the ZRX order in one step
-            const expectedBuyFeeTokensFillResults = await this._forwarderContract.calculateMarketBuyZrxResults.callAsync(
-                params.orders,
-                makerAssetFillAmount,
-            );
-            if (expectedBuyFeeTokensFillResults.makerAssetFilledAmount.lessThan(makerAssetFillAmount)) {
-                throw new Error(INSUFFICENT_ORDERS_FOR_MAKER_AMOUNT);
-            }
-            fillAmountWei = expectedBuyFeeTokensFillResults.takerAssetFilledAmount;
-        } else {
-            const expectedMarketBuyFillResults = await this._forwarderContract.calculateMarketBuyResults.callAsync(
-                params.orders,
-                makerAssetFillAmount,
-            );
-            if (expectedMarketBuyFillResults.makerAssetFilledAmount.lessThan(makerAssetFillAmount)) {
-                throw new Error(INSUFFICENT_ORDERS_FOR_MAKER_AMOUNT);
-            }
-            fillAmountWei = expectedMarketBuyFillResults.takerAssetFilledAmount;
-            const expectedFeeAmount = expectedMarketBuyFillResults.takerFeePaid;
-            if (expectedFeeAmount.greaterThan(ZERO_AMOUNT)) {
-                const expectedFeeFillFillAmountWei = await this._calculateMarketBuyERC20FillAmountAsync(
-                    feeOrders,
-                    [],
-                    DEFAULT_FEE_PROPORTION,
-                    expectedFeeAmount,
-                );
-                fillAmountWei = fillAmountWei.plus(expectedFeeFillFillAmountWei);
-            }
-        }
-        fillAmountWei = ForwarderWrapper._calculateAdditionalFeeProportionAmount(feeProportion, fillAmountWei);
-        return fillAmountWei;
-    }
-    private async _calculateMarketBuyERC721FillAmountAsync(
-        orders: SignedOrder[],
-        feeOrders: SignedOrder[],
-        feeProportion: number,
-    ): Promise<BigNumber> {
-        // Total cost when buying ERC721 is the total cost of all ERC721 orders + any fee abstraction
-        let fillAmountWei = _.reduce(
-            orders,
-            (totalAmount: BigNumber, order: SignedOrder) => {
-                return totalAmount.plus(order.takerAssetAmount);
-            },
-            ZERO_AMOUNT,
-        );
-        const totalFees = _.reduce(
-            orders,
-            (totalAmount: BigNumber, order: SignedOrder) => {
-                return totalAmount.plus(order.takerFee);
-            },
-            ZERO_AMOUNT,
-        );
-        if (totalFees.greaterThan(ZERO_AMOUNT)) {
-            // Calculate the ZRX fee abstraction cost
-            const emptyFeeOrders: SignedOrder[] = [];
-            const expectedFeeAmountWei = await this._calculateMarketBuyERC20FillAmountAsync(
-                feeOrders,
-                emptyFeeOrders,
-                DEFAULT_FEE_PROPORTION,
-                totalFees,
-            );
-            fillAmountWei = fillAmountWei.plus(expectedFeeAmountWei);
-        }
-        fillAmountWei = ForwarderWrapper._calculateAdditionalFeeProportionAmount(feeProportion, fillAmountWei);
-        return fillAmountWei;
+    public async withdrawERC20Async(
+        tokenAddress: string,
+        amount: BigNumber,
+        txData: TxDataPayable,
+    ): Promise<TransactionReceiptWithDecodedLogs> {
+        const txHash = await this._forwarderContract.withdrawERC20.sendTransactionAsync(tokenAddress, amount, txData);
+        const tx = await this._logDecoder.getTxWithDecodedLogsAsync(txHash);
+        return tx;
     }
 }
diff --git a/packages/types/src/index.ts b/packages/types/src/index.ts
index 19f2b1a23..555cd7dec 100644
--- a/packages/types/src/index.ts
+++ b/packages/types/src/index.ts
@@ -215,10 +215,10 @@ export enum RevertReason {
     LibBytesGreaterOrEqualToSourceBytesLengthRequired = 'GREATER_OR_EQUAL_TO_SOURCE_BYTES_LENGTH_REQUIRED',
     Erc20InsufficientBalance = 'ERC20_INSUFFICIENT_BALANCE',
     Erc20InsufficientAllowance = 'ERC20_INSUFFICIENT_ALLOWANCE',
-    UnacceptableThreshold = 'UNACCEPTABLE_THRESHOLD',
-    FeeProportionTooLarge = 'FEE_PROPORTION_TOO_LARGE',
+    FeePercentageTooLarge = 'FEE_PERCENTAGE_TOO_LARGE',
     ValueGreaterThanZero = 'VALUE_GREATER_THAN_ZERO',
     InvalidMsgValue = 'INVALID_MSG_VALUE',
+    InsufficientEthRemaining = 'INSUFFICIENT_ETH_REMAINING',
 }
 
 export enum StatusCodes {
diff --git a/packages/web3-wrapper/CHANGELOG.json b/packages/web3-wrapper/CHANGELOG.json
index d707ef486..975f83037 100644
--- a/packages/web3-wrapper/CHANGELOG.json
+++ b/packages/web3-wrapper/CHANGELOG.json
@@ -1,5 +1,14 @@
 [
     {
+        "version": "1.1.0",
+        "changes": [
+            {
+                "note": "Add `getTransactionByHashAsync` method",
+                "pr": 847
+            }
+        ]
+    },
+    {
         "timestamp": 1532357734,
         "version": "1.0.1",
         "changes": [
diff --git a/packages/web3-wrapper/src/web3_wrapper.ts b/packages/web3-wrapper/src/web3_wrapper.ts
index 883a99bb4..dd35e2094 100644
--- a/packages/web3-wrapper/src/web3_wrapper.ts
+++ b/packages/web3-wrapper/src/web3_wrapper.ts
@@ -14,6 +14,7 @@ import {
     Provider,
     RawLogEntry,
     TraceParams,
+    Transaction,
     TransactionReceipt,
     TransactionReceiptWithDecodedLogs,
     TransactionTrace,
@@ -221,6 +222,19 @@ export class Web3Wrapper {
         return transactionReceipt;
     }
     /**
+     * Retrieves the transaction data for a given transaction
+     * @param txHash Transaction hash
+     * @returns The raw transaction data
+     */
+    public async getTransactionByHashAsync(txHash: string): Promise<Transaction> {
+        assert.isHexString('txHash', txHash);
+        const transaction = await this._sendRawPayloadAsync<Transaction>({
+            method: 'eth_getTransactionByHash',
+            params: [txHash],
+        });
+        return transaction;
+    }
+    /**
      * Retrieves an accounts Ether balance in wei
      * @param owner Account whose balance you wish to check
      * @returns Balance in wei