The Fail Zero complete bolt carrier is the BCG that you want to put in your rifle. The Fail Zero BCG's are assembled and ready to drop into your mil-spec upper receiver. This particular version is the full auto carrier which features a standard black nitride coating. All criticl parts are Black Salt Bath Nitride Finished in order to provide enhanced durability and increases the overall life for both wear and corrosion resistance. Additionally noteworthy is the fact that this unit comes with a firing pin which features a chrome finish.