9mm AR-15 buffer spacer to limit overtravel of the bolt carrier. Preventing bolt catch breakage and providing a smoother shooting gun Limits the overall travel of the bolt carrier to prevent bolt catch breakage Retaining pin slot allows for easy insertion and removal without the use of a tool Made from 6061 aluminum and features a black nitride finish Compatible with both GLOCK(R) and Colt(R) 9mm AR-15's For use with a AR-15 carbine spring