Failzero Fail Zero Bolt Carrier Group BCG 5.56mm Black Nitride Ar-15. 56 Black Nitride BCG Specifications for Failzero Fail Zero Bolt Carrier Group (BCG) 5.56mm Black Nitride Ar-15: Manufacturer: FailZero Color: Black Finish: Nitride Fabric/Material: Steel Carrier Material: 8620 Steel Bolt Material: Steel Gun Make: AR Platform Gun Model: AR-15 Condition: New Package Contents: Failzero Fail Zero Bolt Carrier Group 5.56mm Black Nitride Ar-15 What firearm models does the manufacturer say Failzero Fail Zero Bolt Carrier Group (BCG) 5.56mm Black Nitride Ar-15 is compatible with? The manufacturer says that Failzero Fail Zero Bolt Carrier Group (BCG) 5.56mm Black Nitride Ar-15 is compatible with AR-15Failzero Fail Zero Bolt Carrier Group 5.56mm Black Nitride Ar-15