DoubleStar M-16 Full-Auto Bolt Carrier Group BCG Black. made from 8620 Steel and coated per Mil-Spec. Assembly includes a staked gas key chrome-lined carrier and gas key and bolt assembly. 9mm does not require bolt. Specifications for DoubleStar M-16 Full-Auto Bolt Carrier Group (BCG): Manufacturer: DoubleStar Color: Black Fabric/Material: Steel Carrier Material: 8620 Steel Bolt Material: Steel Caliber: 5.56x45mm NATO Gun Model: M16 Hand: Right Condition: New Features of DoubleStar M-16 Full-Auto Bolt Carrier Group BCG M16 Stripped/Assembly: Assembly Complete w/bolt bolt carrier and firing pin Staked gas key Chromed line carrier and gas key Staked gas key Package Contents: DoubleStar M-16 Full-Auto Bolt Carrier Group (BCG) What firearm models does the manufacturer say DoubleStar M-16 Full-Auto Bolt Carrier Group (BCG) is compatible with? The manufacturer says that DoubleStar M-16 Full-Auto Bolt Carrier Group (BCG) is compatible with M16DoubleStar AR100M: M-16 Full-Auto Bolt Carrier Group Black