Daniel Defense 5.56 NATO (5.56x45mm & .223 Remington) / 300 Blackout (7.6x35mm) full-auto compatible, M16 Profile, complete bolt carrier group assembly. Carrier: Machined from 8620 steel Heavy Phosphate Coated Chrome lined Properly staked gas keys Made in the USA Bolt: Machined from Carpenter 158 Steel High Pressure Tested Magnetic Particle Inspected Shot Peened Heavy Phosphate Coated Extractor Booster Made in the USA