Pistol Buffer Assembly Kit for AR-15 The package comes with a Mil-Spec anodized aluminum pistol receiver extension, steel endplate, castle nut, buffer, and buffer spring. The lightweight assembly will ensure that your pistol stays slim and agile, and the tube’s ergonomics will magnify comfort and efficiency while shooting. The tube also comes with a high-density foam sleeve for improved grip and comfort. Material: Aircraft Grade Aluminum / Steel Mounting Hardware Finish: Black Anodized