Bravo Company, MK2 Receiver Extension, Fits AR, Buffer Tube, Matte Finish, BlackBCM MK2 Receiver Extension for your AR15" M16" M4. Machined from 7075T6 and manufactured to Mil Spec dimensions and specifications. Mil Spec receiver extensions have a slightly smaller dimension where the stock slides on. *NOTE* These buffer tubes require a rifle action spring and specific BCM MK2 buffer, carbine and rifle buffers will NOT work. Features : Fits AR 8 Position Can Reduce Felt Recoil Requires Proprietary Buffer Weight UPC 812526023599