A standalone firing pin might not make much sense to those used to buying complete bolts, but it never hurts to have extra components on-hand in a pinch! This is a mil-spec firing pin designed for use in standard AR-15 bolt-carrier groups. It's inexpensive, it works, and it's new-manufacture, so it's worth having a spare around, just in case something happens to the firing pin in your gun. Mfg: Cmmg