The angstadt arms ar-15 bolt carrier group is machined from 8620 alloy steel with a qpq black nitride finish.It features a removable weight for use with law tactical folding stock adapter and is compatible with both glock and colt 9mm ar-15 magazines.Use with a standard ar-15 hammer.Finish: QPQ Black NitrideType: Bolt Carrier GroupModel: Bolt Carrier AssemblySize: 9mmMaterial: 8620 Steel