Keep your firearms in working order with the Breakthrough Clean Technologies AR-10 .308 Caliber and 7.62mm Nylon Bolt Carrier Key Brush. Featuring stiff nylon bristles to combat heavy fouling, this brush comes with a rugged brass core for durability. Breakthrough Clean Technologies AR-10 .308 Caliber and 7.62mm Nylon Bolt Carrier Key Brush - Gun Cleaning at Academy Sports