The American Built Arms AR-15 Essential Parts Kit is comprised of genuine, Mil-spec, high quality parts for those AR-15/M-16 small parts that wear down, break, or simply get lost. With this Essentials Kit on hand, you'll always have the parts you need to keep your rifle running smoothly. These high-quality parts are manufactured to precise tolerances to ensure a correct fit with your AR-15 rifle. This convenient kit contains all the parts needed to keep your 5.56 AR-15/M-16 rifle like new. Included:Nickel-boron coated cam pinChrome firing pinFiring pin retaining pinEjectorEjector springEjector pinExtractor spring with insertExtractor axleGas ringsRubber O ring