Made with 8620 AISI steel and boasting a NIB/Mag-phosphate finish, the Stern bolt fits into Mil-Spec and Glock-pattern upper receivers. It functions with Colt SMG, Glock magazines and it's fully compatible with standard AR15/M16 charging handles. Comes fully assembled with all sub-components installed, including firing pin/spring/retaining pin, extractor, and extractor spring. Also included in bolt assembly is a propriety center and roll pins. The 9mm bolts incorporate the new bolt design which caters to single stage triggers with short resets.