For enhanced and noticeably smoother operation of the Windham Weaponry MCS System in 9MM caliber mode, this new, upgraded 9mm buffer offers several side benefits: smoother function, less felt recoil, increased reliability, more consistent cycling, and a reduced rate of fire. While we recommend this buffer for our Multi-Caliber System, it will improve the function of any AR platform 9mm rifle. The buffer installs the same as any regular AR-15 buffer. It is machined from high quality stainless steel and utilizes standard AR-15 H2 buffer internals. To help with identification while installed, the face has been stamped â€œ9mmâ€. Weight is 8.4 oz. Made in the USA. For those MCS System owners, call us for special pricing on this upgrade buffer.