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.The 45 bolts incorporate the new bolt design which caters to single stage triggers with short resets.Finish: Mag PhosphateMaterial: 8620 Steel