diff --git a/src/CBAppClient.ts b/src/CBAppClient.ts
index 0cde0cb..f6fe4c4 100644
--- a/src/CBAppClient.ts
+++ b/src/CBAppClient.ts
@@ -31,7 +31,13 @@ export class CBAppClient extends BaseRestClient {
     restClientOptions: RestClientOptions = {},
     requestOptions: AxiosRequestConfig = {},
   ) {
-    super(restClientOptions, requestOptions);
+    super(restClientOptions, {
+      ...requestOptions,
+      headers: {
+        'CB-VERSION': '2024-09-13',
+        ...requestOptions.headers,
+      },
+    });
     return this;
   }
 
diff --git a/src/lib/BaseRestClient.ts b/src/lib/BaseRestClient.ts
index 336b624..11faebe 100644
--- a/src/lib/BaseRestClient.ts
+++ b/src/lib/BaseRestClient.ts
@@ -150,6 +150,7 @@ export abstract class BaseRestClient {
       /** inject custom rquest options based on axios specs - see axios docs for more guidance on AxiosRequestConfig: https://github.com/axios/axios#request-config */
       ...networkOptions,
       headers: {
+        ...networkOptions.headers,
         'Content-Type': 'application/json',
         locale: 'en-US',
         'User-Agent': USER_AGENT,
@@ -175,11 +176,7 @@ export abstract class BaseRestClient {
       });
     }
 
-    this.baseUrl = getRestBaseUrl(
-      false,
-      restClientOptions,
-      this.getClientType(),
-    );
+    this.baseUrl = getRestBaseUrl(restClientOptions, this.getClientType());
 
     this.apiKey = this.options.apiKey;
     this.apiSecret = this.options.apiSecret;
diff --git a/src/lib/requestUtils.ts b/src/lib/requestUtils.ts
index bdbecfa..a9a3965 100644
--- a/src/lib/requestUtils.ts
+++ b/src/lib/requestUtils.ts
@@ -25,12 +25,22 @@ const exchangeBaseURLMap = {
   [REST_CLIENT_TYPE_ENUM.advancedTrade]: 'https://api.coinbase.com',
   [REST_CLIENT_TYPE_ENUM.coinbaseApp]: 'https://api.coinbase.com',
   [REST_CLIENT_TYPE_ENUM.exchange]: 'https://api.exchange.coinbase.com',
-  [REST_CLIENT_TYPE_ENUM.prime]: 'https://api.prime.coinbase.com', // /v1
+  [REST_CLIENT_TYPE_ENUM.prime]: 'https://api.prime.coinbase.com',
   [REST_CLIENT_TYPE_ENUM.international]:
     'https://api.international.coinbase.com',
   [REST_CLIENT_TYPE_ENUM.commerce]: 'https://api.commerce.coinbase.com',
 } as const;
 
+const exchangeSandboxURLMap = {
+  [REST_CLIENT_TYPE_ENUM.exchange]:
+    'https://api-public.sandbox.exchange.coinbase.com',
+  [REST_CLIENT_TYPE_ENUM.international]: 'https://api-n5e1.coinbase.com',
+  [REST_CLIENT_TYPE_ENUM.advancedTrade]: 'NoSandboxAvailable',
+  [REST_CLIENT_TYPE_ENUM.coinbaseApp]: 'NoSandboxAvailable',
+  [REST_CLIENT_TYPE_ENUM.prime]: 'NoSandboxAvailable',
+  [REST_CLIENT_TYPE_ENUM.commerce]: 'NoSandboxAvailable',
+} as const;
+
 export interface RestClientOptions {
   /**
    * Your API key name.
@@ -85,6 +95,18 @@ export interface RestClientOptions {
     | 'pt'
     | 'pt-br';
 
+  /**
+   * Connect to the sandbox for supported products
+   *
+   * - Coinbase Exchange: https://docs.cdp.coinbase.com/exchange/docs/sandbox
+   * - Coinbase International: https://docs.cdp.coinbase.com/intx/docs/sandbox
+   *
+   * - Coinbase App: No sandbox available.
+   * - Coinbase Advanced Trade: No sandbox available.
+   * - Coinbase Prime: No sandbox available.
+   */
+  useSandbox?: boolean;
+
   /**
    * Enable keep alive for REST API requests (via axios).
    * See: https://github.com/tiagosiebler/bybit-api/issues/368
@@ -159,20 +181,19 @@ export function logInvalidOrderId(
 }
 
 export function getRestBaseUrl(
-  useTestnet: boolean,
-  restInverseOptions: RestClientOptions,
+  restClientOptions: RestClientOptions,
   restClientType: RestClientType,
 ): string {
   const exchangeBaseUrls = {
     livenet: exchangeBaseURLMap[restClientType],
-    testnet: 'https://noTestnet',
+    testnet: exchangeSandboxURLMap[restClientType],
   };
 
-  if (restInverseOptions.baseUrl) {
-    return restInverseOptions.baseUrl;
+  if (restClientOptions.baseUrl) {
+    return restClientOptions.baseUrl;
   }
 
-  if (useTestnet) {
+  if (restClientOptions.useSandbox === true) {
     return exchangeBaseUrls.testnet;
   }