Complete, drop-in carrier/bolt assembly is ramped on the bottom to provide clearance for a factory .223/5.56mm hammer in your 9mm conversion. Eliminates the need to install a dedicated 9mm hammer, so the original fire control system stays intact for easier conversion back to original caliber. Precision machined from high-grade ordnance steel, the one-piece design combines bolt and carrier as a single unit to provide outstanding strength, durability, and reliability. Includes a staked-on carrier key. Does Not Work With Glock Magazines Mfg: Cmmg SPECS: Steel, black oxide finish. Fits rifles and carbines with Rock River Arms and Colt-style 9mm blow back system.