diff --git a/src/kulap.ts b/src/kulap.ts
index a6e8f70..8e9d860 100644
--- a/src/kulap.ts
+++ b/src/kulap.ts
@@ -1,7 +1,7 @@
 import axios, { AxiosError } from 'axios';
 import Web3 from "web3"
 import { ethers } from 'ethers'
-import { Network, Configuration, APIError, TradeOptions, Rate, Options } from "./types"
+import { GasOption, Network, Configuration, APIError, TradeOption, TradeOptions, Rate, Options } from "./types"
 import { SUPPORTED_TOKENS, API_BASE_URL, KULAP_DEX_CONTRACT } from "./constants"
 import { kulapAbi } from "./abi"
 import { resolveContractAddress, resolveTokenDecimals, constructGasOptions, defaultGasOptions } from "./utils"
@@ -26,6 +26,13 @@ export class Kulap {
         }
     }
 
+    private getGasOption(option: TradeOption): GasOption {
+        return {
+            gasLimit: `${option.gasLimit}`,
+            gasPrice: `${this.web3.utils.toWei(option.gasPrice, "gwei")}`
+        }
+    }
+
     async getNetworkId(): Promise<Number> {
         try {
             return await this.web3.eth.net.getId()
@@ -63,13 +70,6 @@ export class Kulap {
                 }
             })
             const tradeOptions: TradeOptions = response.data
-            
-            const reduceOption = (option: any) => {
-                return {
-                    gasLimit: option.gasLimit,
-                    gasPrice: `${this.web3.utils.toWei(option.gasPrice, "gwei")}`
-                }
-            }
 
             return {
                 rate: tradeOptions["STD"].trade.rate,
@@ -79,9 +79,9 @@ export class Kulap {
                 toAmount: tradeOptions["STD"].trade.toAmount,
                 toSymbol: targetToken,
                 gasOptions: {
-                    "FAST": reduceOption(tradeOptions["FAST"]),
-                    "STD": reduceOption(tradeOptions["STD"]),
-                    "SLOW": reduceOption(tradeOptions["SLOW"])
+                    "FAST": this.getGasOption(tradeOptions["FAST"]),
+                    "STD": this.getGasOption(tradeOptions["STD"]),
+                    "SLOW": this.getGasOption(tradeOptions["SLOW"])
                 }
             }
         } catch (e) {
@@ -108,13 +108,6 @@ export class Kulap {
                 }
             })
             const tradeOptions: TradeOptions = response.data
-            
-            const reduceOption = (option: any) => {
-                return {
-                    gasLimit: option.gasLimit,
-                    gasPrice: `${this.web3.utils.toWei(option.gasPrice, "gwei")}`
-                }
-            }
 
             return {
                 rate: tradeOptions["STD"].trade.rate,
@@ -124,9 +117,9 @@ export class Kulap {
                 toAmount: tradeOptions["STD"].trade.toAmount,
                 toSymbol: targetToken,
                 gasOptions: {
-                    "FAST": reduceOption(tradeOptions["FAST"]),
-                    "STD": reduceOption(tradeOptions["STD"]),
-                    "SLOW": reduceOption(tradeOptions["SLOW"])
+                    "FAST": this.getGasOption(tradeOptions["FAST"]),
+                    "STD": this.getGasOption(tradeOptions["STD"]),
+                    "SLOW": this.getGasOption(tradeOptions["SLOW"])
                 }
             }
         } catch (e) {
@@ -198,14 +191,15 @@ export class Kulap {
             // @ts-ignore
             const dexContract = new this.web3.eth.Contract(kulapAbi, KULAP_DEX_CONTRACT)
             const currentAccount = await this.getAccount()
-            let gasOptions = (options && options.gasOptions) ? constructGasOptions(options.gasOptions, rate) : defaultGasOptions(rate)
-            // Supply value when the source is native ETH
-            if (rate.fromSymbol === "ETH") {
-                gasOptions = {
-                    value: rate.fromAmount,
-                    ...gasOptions,
-                }
+            const gasOption = (options && options.gasOptions) ? constructGasOptions(options.gasOptions, rate) : defaultGasOptions(rate)
+            const payload = {
+                gasLimit: gasOption.gasLimit,
+                gasPrice: gasOption.gasPrice,
             }
+    
+            // Supply value when the source is native ETH
+            if (rate.fromSymbol === "ETH") Object.assign(payload, { value: rate.fromAmount })
+
             const tradingProxyIndex = rate.routes[0]
             const fromAddress = resolveContractAddress(rate.fromSymbol)
             const toAddress = resolveContractAddress(rate.toSymbol)
@@ -227,7 +221,7 @@ export class Kulap {
                 options && options.partnerId ? options.partnerId : 0
             ).send({
                 from: currentAccount,
-                ...gasOptions
+                ...payload
             })
 
             return tx
diff --git a/src/types/TradeOptions.ts b/src/types/TradeOptions.ts
index 779b83e..fd9badf 100644
--- a/src/types/TradeOptions.ts
+++ b/src/types/TradeOptions.ts
@@ -1,4 +1,4 @@
-import { Options } from "./Web3"
+import { GasOption } from "./Web3"
 
 type Trade = {
     routes: number[]
@@ -7,7 +7,7 @@ type Trade = {
     rate: string
 }
 
-type TradeOption = {
+export type TradeOption = {
     gasPrice: string
     gasLimit: number
     trade: Trade
@@ -27,9 +27,9 @@ export type Rate = {
     toAmount: string
     toSymbol : string
     gasOptions: {
-        "FAST": Options,
-        "STD": Options,
-        "SLOW": Options
+        "FAST": GasOption,
+        "STD": GasOption,
+        "SLOW": GasOption
     }
 }
 
diff --git a/src/types/Web3.ts b/src/types/Web3.ts
index a3499a9..0d60641 100644
--- a/src/types/Web3.ts
+++ b/src/types/Web3.ts
@@ -30,7 +30,7 @@
 //     from?: string,
 // ) => Promise<Web3Signature>;
 
-export interface Options {
+export interface GasOption {
     readonly gasLimit: string;
     readonly gasPrice: any;
 }
diff --git a/src/types/index.ts b/src/types/index.ts
index 8ba22ad..f3e04a5 100644
--- a/src/types/index.ts
+++ b/src/types/index.ts
@@ -1,5 +1,6 @@
 
-import { TradeOptions, Rate } from "./TradeOptions"
+import { GasOption } from './Web3'
+import { TradeOption, TradeOptions, Rate } from "./TradeOptions"
 import { Configuration, Network } from "./Configuration"
 
 
@@ -15,6 +16,8 @@ export type Options = {
 }
 
 export {
+    GasOption,
+    TradeOption,
     TradeOptions,
     Configuration,
     Network,
diff --git a/src/utils/index.ts b/src/utils/index.ts
index 6c6f1be..f5eeeaf 100644
--- a/src/utils/index.ts
+++ b/src/utils/index.ts
@@ -1,5 +1,5 @@
 import { TOKEN_ADDRESSES, TOKEN_DECIMALS } from "../constants"
-import { Options } from "../types/Web3"
+import { GasOption } from "../types/Web3"
 import { Rate } from "../types"
 
 export const resolveContractAddress = (symbol: string): String => {
@@ -12,7 +12,7 @@ export const resolveTokenDecimals = (symbol: string): Number => {
     return TOKEN_DECIMALS[symbol] ? TOKEN_DECIMALS[symbol] : 18
 }
 
-export const constructGasOptions = (option: string, rate: Rate): any => {
+export const constructGasOptions = (option: string, rate: Rate): GasOption => {
     switch (option) {
         case "FAST":
             return rate.gasOptions["FAST"]
@@ -23,6 +23,6 @@ export const constructGasOptions = (option: string, rate: Rate): any => {
     }
 }
 
-export const defaultGasOptions = (rate: Rate): any => {
+export const defaultGasOptions = (rate: Rate): GasOption => {
     return rate.gasOptions["FAST"]
 }
\ No newline at end of file