diff --git a/lib/bcoin/mtx.js b/lib/bcoin/mtx.js
index 235db915..97f3f7e9 100644
--- a/lib/bcoin/mtx.js
+++ b/lib/bcoin/mtx.js
@@ -63,6 +63,7 @@ function MTX(options) {
     options = {};
 
   this.version = options.version || 1;
+  this.flag = options.flag || 1;
   this.inputs = [];
   this.outputs = [];
   this.locktime = 0;
diff --git a/lib/bcoin/tx.js b/lib/bcoin/tx.js
index 1b8fb2fa..342008ff 100644
--- a/lib/bcoin/tx.js
+++ b/lib/bcoin/tx.js
@@ -56,6 +56,7 @@ function TX(data) {
 
   assert(data, 'TX data is required.');
   assert(typeof data.version === 'number');
+  assert(typeof data.flag === 'number');
   assert(Array.isArray(data.inputs));
   assert(Array.isArray(data.outputs));
   assert(typeof data.locktime === 'number');
@@ -1429,7 +1430,8 @@ TX.prototype.getModifiedSize = function getModifiedSize(size) {
  * @param {Number?} size - Size to calculate priority
  * based on. If not present, modified size will be
  * calculated and used.
- * @returns {Number} priority
+ * @returns {Object} data - Object containing
+ * `priority` and `value`.
  */
 
 TX.prototype.getPriority = function getPriority(height, size) {
@@ -1485,7 +1487,7 @@ TX.prototype.getPriority = function getPriority(height, size) {
  */
 
 TX.prototype.isFree = function isFree(height, size) {
-  var priority;
+  var data;
 
   if (height == null) {
     height = this.height;
@@ -1493,9 +1495,9 @@ TX.prototype.isFree = function isFree(height, size) {
       height = bcoin.network.get().height + 1;
   }
 
-  priority = this.getPriority(height, size).priority;
+  data = this.getPriority(height, size);
 
-  return priority > constants.tx.FREE_THRESHOLD;
+  return data.priority > constants.tx.FREE_THRESHOLD;
 };
 
 /**
@@ -1528,38 +1530,6 @@ TX.prototype.getRate = function getRate(size) {
   return TX.getRate(size, this.getFee());
 };
 
-/**
- * Calculate minimum fee based on rate and size.
- * @param {Number?} size
- * @param {Rate?} rate - Rate of satoshi per kB.
- * @returns {Amount} fee
- */
-
-TX.getMinFee = function getMinFee(size, rate) {
-  var fee;
-
-  if (rate == null)
-    rate = constants.tx.MIN_RELAY;
-
-  fee = Math.floor(rate * size / 1000);
-
-  if (fee === 0 && rate > 0)
-    fee = rate;
-
-  return fee;
-};
-
-/**
- * Calculate a fee rate based on size and fees.
- * @param {Number} size
- * @param {Amount} fee
- * @returns {Rate}
- */
-
-TX.getRate = function(size, fee) {
-  return Math.floor(fee * 1000 / size);
-};
-
 /**
  * Calculate the minimum fee in order for the transaction
  * to be relayable, but _round to the nearest kilobyte
@@ -1730,6 +1700,38 @@ TX.prototype.__defineGetter__('wtxid', function() {
   return this.rwhash;
 });
 
+/**
+ * Calculate minimum fee based on rate and size.
+ * @param {Number?} size
+ * @param {Rate?} rate - Rate of satoshi per kB.
+ * @returns {Amount} fee
+ */
+
+TX.getMinFee = function getMinFee(size, rate) {
+  var fee;
+
+  if (rate == null)
+    rate = constants.tx.MIN_RELAY;
+
+  fee = Math.floor(rate * size / 1000);
+
+  if (fee === 0 && rate > 0)
+    fee = rate;
+
+  return fee;
+};
+
+/**
+ * Calculate a fee rate based on size and fees.
+ * @param {Number} size
+ * @param {Amount} fee
+ * @returns {Rate}
+ */
+
+TX.getRate = function(size, fee) {
+  return Math.floor(fee * 1000 / size);
+};
+
 /**
  * Inspect the transaction and return a more
  * user-friendly representation of the data.
@@ -1739,8 +1741,8 @@ TX.prototype.__defineGetter__('wtxid', function() {
 TX.prototype.inspect = function inspect() {
   return {
     type: 'tx',
-    hash: utils.revHex(this.hash('hex')),
-    witnessHash: utils.revHex(this.witnessHash('hex')),
+    hash: this.rhash,
+    witnessHash: this.rwhash,
     size: this.getSize(),
     virtualSize: this.maxSize(),
     height: this.height,
@@ -1757,6 +1759,7 @@ TX.prototype.inspect = function inspect() {
     index: this.index,
     changeIndex: this.changeIndex || -1,
     version: this.version,
+    flag: this.flag,
     inputs: this.inputs,
     outputs: this.outputs,
     locktime: this.locktime
@@ -1783,6 +1786,7 @@ TX.prototype.toJSON = function toJSON() {
     index: this.index,
     changeIndex: this.changeIndex || -1,
     version: this.version,
+    flag: this.flag,
     inputs: this.inputs.map(function(input) {
       return input.toJSON();
     }),
@@ -1811,6 +1815,7 @@ TX.parseJSON = function fromJSON(json) {
     index: json.index,
     changeIndex: json.changeIndex || -1,
     version: json.version,
+    flag: json.flag,
     inputs: json.inputs.map(function(input) {
       return bcoin.input.parseJSON(input);
     }),
diff --git a/scripts/gen.js b/scripts/gen.js
index 0def9546..0c5be4af 100644
--- a/scripts/gen.js
+++ b/scripts/gen.js
@@ -30,6 +30,7 @@ function createGenesisBlock(options) {
 
   tx = {
     version: 1,
+    flag: 1,
     inputs: [{
       prevout: {
         hash: constants.NULL_HASH,
diff --git a/test/script-test.js b/test/script-test.js
index f92bff08..f1a51782 100644
--- a/test/script-test.js
+++ b/test/script-test.js
@@ -297,6 +297,7 @@ describe('Script', function() {
       it('should handle script test' + suffix + ': ' + comments, function() {
         var coin = bcoin.tx({
           version: 1,
+          flag: 1,
           inputs: [{
             prevout: {
               hash: constants.NULL_HASH,
@@ -315,6 +316,7 @@ describe('Script', function() {
         });
         var tx = bcoin.tx({
           version: 1,
+          flag: 1,
           inputs: [{
             prevout: {
               hash: coin.hash('hex'),
diff --git a/test/tx-test.js b/test/tx-test.js
index 8940a984..834fe809 100644
--- a/test/tx-test.js
+++ b/test/tx-test.js
@@ -306,6 +306,7 @@ describe('TX', function() {
   it('should fail on >51 bit coin values', function() {
     var tx = bcoin.tx({
       version: 1,
+      flag: 1,
       inputs: [createInput(constants.MAX_MONEY + 1)],
       outputs: [{
         script: [],
@@ -320,6 +321,7 @@ describe('TX', function() {
   it('should handle 51 bit coin values', function() {
     var tx = bcoin.tx({
       version: 1,
+      flag: 1,
       inputs: [createInput(constants.MAX_MONEY)],
       outputs: [{
         script: [],
@@ -334,6 +336,7 @@ describe('TX', function() {
   it('should fail on >51 bit output values', function() {
     var tx = bcoin.tx({
       version: 1,
+      flag: 1,
       inputs: [createInput(constants.MAX_MONEY)],
       outputs: [{
         script: [],
@@ -348,6 +351,7 @@ describe('TX', function() {
   it('should handle 51 bit output values', function() {
     var tx = bcoin.tx({
       version: 1,
+      flag: 1,
       inputs: [createInput(constants.MAX_MONEY)],
       outputs: [{
         script: [],
@@ -362,6 +366,7 @@ describe('TX', function() {
   it('should fail on >51 bit fees', function() {
     var tx = bcoin.tx({
       version: 1,
+      flag: 1,
       inputs: [createInput(constants.MAX_MONEY + 1)],
       outputs: [{
         script: [],
@@ -376,6 +381,7 @@ describe('TX', function() {
   it('should fail on >51 bit values from multiple', function() {
     var tx = bcoin.tx({
       version: 1,
+      flag: 1,
       inputs: [
         createInput(Math.floor(constants.MAX_MONEY / 2)),
         createInput(Math.floor(constants.MAX_MONEY / 2)),
@@ -394,6 +400,7 @@ describe('TX', function() {
   it('should fail on >51 bit output values from multiple', function() {
     var tx = bcoin.tx({
       version: 1,
+      flag: 1,
       inputs: [createInput(constants.MAX_MONEY)],
       outputs: [
         {
@@ -418,6 +425,7 @@ describe('TX', function() {
   it('should fail on >51 bit fees from multiple', function() {
     var tx = bcoin.tx({
       version: 1,
+      flag: 1,
       inputs: [
         createInput(Math.floor(constants.MAX_MONEY / 2)),
         createInput(Math.floor(constants.MAX_MONEY / 2)),
@@ -439,6 +447,7 @@ describe('TX', function() {
     for (var i = 0; i < 3; i++) {
       var tx = bcoin.tx({
         version: 1,
+        flag: 1,
         inputs: [
           createInput(Math.floor(constants.MAX_MONEY / 2))
         ],
@@ -456,6 +465,7 @@ describe('TX', function() {
   it('should fail to parse >53 bit values', function() {
     var tx = bcoin.tx({
       version: 1,
+      flag: 1,
       inputs: [
         createInput(Math.floor(constants.MAX_MONEY / 2))
       ],
@@ -483,6 +493,7 @@ describe('TX', function() {
   it('should fail on 53 bit coin values', function() {
     var tx = bcoin.tx({
       version: 1,
+      flag: 1,
       inputs: [createInput(utils.MAX_SAFE_INTEGER)],
       outputs: [{
         script: [],
@@ -497,6 +508,7 @@ describe('TX', function() {
   it('should fail on 53 bit output values', function() {
     var tx = bcoin.tx({
       version: 1,
+      flag: 1,
       inputs: [createInput(constants.MAX_MONEY)],
       outputs: [{
         script: [],
@@ -511,6 +523,7 @@ describe('TX', function() {
   it('should fail on 53 bit fees', function() {
     var tx = bcoin.tx({
       version: 1,
+      flag: 1,
       inputs: [createInput(utils.MAX_SAFE_INTEGER)],
       outputs: [{
         script: [],
@@ -526,6 +539,7 @@ describe('TX', function() {
     it('should fail on >53 bit values from multiple', function() {
       var tx = bcoin.tx({
         version: 1,
+        flag: 1,
         inputs: [
           createInput(MAX),
           createInput(MAX),
@@ -544,6 +558,7 @@ describe('TX', function() {
     it('should fail on >53 bit output values from multiple', function() {
       var tx = bcoin.tx({
         version: 1,
+        flag: 1,
         inputs: [createInput(constants.MAX_MONEY)],
         outputs: [
           {
@@ -568,6 +583,7 @@ describe('TX', function() {
     it('should fail on >53 bit fees from multiple', function() {
       var tx = bcoin.tx({
         version: 1,
+        flag: 1,
         inputs: [
           createInput(MAX),
           createInput(MAX),
@@ -589,6 +605,7 @@ describe('TX', function() {
       for (var i = 0; i < 3; i++) {
         var tx = bcoin.tx({
           version: 1,
+          flag: 1,
           inputs: [
             createInput(MAX)
           ],