AR-15 Rifle Buffer Kit, No Stock Receiver Extension Kit for Standard Buttstock All the components needed to mount the non-collapsible A1 styles of AR-15 buttstock such as the Magpul PRS and M16-A1. You may need a spacer to use this buffer tube with a buttstock labeled A2 or E2. All parts are manufactured from the highest quality materials and held to strict dimensional tolerances for proper fit and function. Please Note: For these rifle stock buffer kits, these will only come with the buffer tube, the buffer, and the spring. These will not include the back plate and castle nut as those are components that are only needed with a carbine buffer kit.