Made from aluminum with a sleek and durable matte black finish, the CMMGPistol Receiver Extension (Buffer Tube) kit includes what you need to finish up your AR pistol lower. The ambidextrous sling mount end plate makes for quick attachment and easy sling adjustment. Includes: Pistol Buffer Tube Ambi Sling Mount/Receiver End Plate Castle Nut Buffer Action Spring Installation Tools: Due to the difference in the pistol buffer tube diameter compared to mil-spec diameter buffer tubes, thicker castle nut wrenches may not fit between the shoulder of the buffer tube and end of the castle nut. CMMG recommends the use of thin castle nut wrenches such as the Real-Avid Thin Castle Nut Wrench.