Black Rain Ordnance AR-15/M16 Nickel Boron coated complete bolt carrier group. Engraved with the B.R.O. Bio Hazard logo. 

Brand: Black Rain Ordnance
Caliber / Gauge: 5.56 NATO
Carrier Style: M16 / Full-Auto
Platform: AR-15
Bolt Finish: Nickel Boron
Carrier Finish: Nickel Boron
Gas Key: Staked