Tacfire AR15 5.56 NATO Bolt Carrier Group Black. 56 NATO Bolt Carrier Group BCG/MPI Tested Nitride (made in specialized factories) Specifications for Tacfire AR15 5.56 NATO Bolt Carrier Group (BCG): Manufacturer: TacFire Finish: Nitride Carrier Material: 8620 Steel Bolt Material: 9310 Steel Caliber: 5.56x45mm NATO Gun Make: AR Platform Gun Model: AR-15 Hand: Right Weight: 11.7 oz Country of Origin: USA Features of Tacfire AR15 5.56 NATO Bolt Carrier Group BCG: Tacfire AR15 5.56 NATO Bolt Carrier Group BCG Black BCG Package Contents: Tacfire AR15 5.56 NATO Bolt Carrier Group What firearm models does the manufacturer say Tacfire AR15 5.56 NATO Bolt Carrier Group (BCG) is compatible with? The manufacturer says that Tacfire AR15 5.56 NATO Bolt Carrier Group (BCG) is compatible with AR-15Tacfire BCG: AR15 5.56 NATO Bolt Carrier Group Black