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 “9mm”. Weight is 8.4 oz. Made in the USA. For those MCS System owners, call us for special pricing on this upgrade buffer.