diff --git a/CHANGELOG.md b/CHANGELOG.md
index c6a01d9..183b001 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,7 @@
 ### Changed
 - Abstract method `HttpClientPool::chooseHttpClient()` has now an explicit return type (`Http\Client\Common\HttpClientPoolItem`)
 - Interface method `Plugin::handleRequest(...)` has now an explicit return type (`Http\Promise\Promise`)
+- Made all classes final as they are not intended to be extended.
 
 ### Removed
 - Deprecated option `debug_plugins` has been removed from `PluginClient`
diff --git a/src/BatchClient.php b/src/BatchClient.php
index 8dfeb81..38532ed 100644
--- a/src/BatchClient.php
+++ b/src/BatchClient.php
@@ -15,7 +15,7 @@
  *
  * @author Joel Wurtz <jwurtz@jolicode.com>
  */
-class BatchClient implements HttpClient
+final class BatchClient implements HttpClient
 {
     /**
      * @var HttpClient
diff --git a/src/Deferred.php b/src/Deferred.php
index 7413451..c294a8d 100644
--- a/src/Deferred.php
+++ b/src/Deferred.php
@@ -9,7 +9,7 @@
 /**
  * A deferred allow to return a promise which has not been resolved yet.
  */
-class Deferred implements Promise
+final class Deferred implements Promise
 {
     private $value;
 
diff --git a/src/HttpClientPoolItem.php b/src/HttpClientPoolItem.php
index a46ee2f..becde17 100644
--- a/src/HttpClientPoolItem.php
+++ b/src/HttpClientPoolItem.php
@@ -16,7 +16,7 @@
  *
  * @author Joel Wurtz <joel.wurtz@gmail.com>
  */
-class HttpClientPoolItem implements HttpClient, HttpAsyncClient
+final class HttpClientPoolItem implements HttpClient, HttpAsyncClient
 {
     /**
      * @var int Number of request this client is currently sending
diff --git a/src/HttpClientRouter.php b/src/HttpClientRouter.php
index 00ca15f..d4e00df 100644
--- a/src/HttpClientRouter.php
+++ b/src/HttpClientRouter.php
@@ -12,6 +12,8 @@
 /**
  * Route a request to a specific client in the stack based using a RequestMatcher.
  *
+ * This is not a HttpClientPool client because it uses a matcher to select the client.
+ *
  * @author Joel Wurtz <joel.wurtz@gmail.com>
  */
 final class HttpClientRouter implements HttpClient, HttpAsyncClient
@@ -26,9 +28,7 @@ final class HttpClientRouter implements HttpClient, HttpAsyncClient
      */
     public function sendRequest(RequestInterface $request): ResponseInterface
     {
-        $client = $this->chooseHttpClient($request);
-
-        return $client->sendRequest($request);
+        return $this->chooseHttpClient($request)->sendRequest($request);
     }
 
     /**
@@ -36,9 +36,7 @@ public function sendRequest(RequestInterface $request): ResponseInterface
      */
     public function sendAsyncRequest(RequestInterface $request)
     {
-        $client = $this->chooseHttpClient($request);
-
-        return $client->sendAsyncRequest($request);
+        return $this->chooseHttpClient($request)->sendAsyncRequest($request);
     }
 
     /**
diff --git a/src/HttpMethodsClient.php b/src/HttpMethodsClient.php
index bc02ef8..082575a 100644
--- a/src/HttpMethodsClient.php
+++ b/src/HttpMethodsClient.php
@@ -24,7 +24,7 @@
  * @author Márk Sági-Kazár <mark.sagikazar@gmail.com>
  * @author David Buchmann <mail@davidbu.ch>
  */
-class HttpMethodsClient implements HttpClient
+final class HttpMethodsClient implements HttpClient
 {
     /**
      * @var HttpClient