The AR-STONER T-Series Bolt Carrier Group is a great option for your next AR build. Machined to strict mil-spec tolerances, this bolt carrier group is drop-in ready. The Nickel Boron finish provides enhanced reliability and is easy to clean. With a 5.56 bolt face, this Bolt Carrier Group is ideal for your next rifle. Note: Upon installation, headspace should be verified by a qualified gunsmith. Features8620 Steel Carrier9310 Steel Bolt HPT/MPINiB coated carrier/boltMagnetic Particle InspectedShot PeenedSerrated for use with Forward Assist17-4 Stainless Steel Gas Key S-7 shock resisting tool steel ExtractorStaked Gas Key17-4 stainless steel firing pin