This AR-15 firing pin is enhanced with solid chrome plating. They are precision-machined high-quality 4140 steel firing pins for AR-15, M4 and M16 rifles. It has a hard, solid chrome finish to increase firing pin longevity and make cleaning easier. The AR-15 firing pin fits AR-15.233/5.56 NATO Bolt Carrier Groups. This AR-15 firing pin is made from solid chrome-plated 4140 alloy steel, which is considerably stronger than standard steel.