Made with 8620 AISI steel and boasting a 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. Our 9mm bolts incorporate our new bolt design which caters to single stage triggers with short resets. It also allows use with the JP silent capture spring.