This 9mm Bolt Carrier Group (BCG) comes fully assembled and ready to drop into most 9mm AR platform rifles and pistols. The FailZero Black Nitride 9mm BCG is compatible with both lowers designated for Glock or Colt magazines. All critical parts are coated with Salt Bath Nitride (Black) which provides durability and increases both wear and corrosion resistance.Details:* FZ 9MM BCG is compatible with both Glock and Colt style magazines* 8620 heat treated (same as Mil-Spec) AR Carrier* Black Nitride Finish (Salt Bath Nitride)* Staked carrier guide (gas key)* 5.56 Extractor* Chrome Firing Pin