Complete bolt carrier group (BCG). 5.56x45, 223, & related calibers. EXO technology, A revolutionary surface that provides permanent dry lubricity, radically improves the performance of your AR-15 and eliminates the need to apply oil or grease to treated parts for the life of the weapon. Treaded parts: bolt, bolt carrier, extractor, cam pin, carrier key, & firing pin. Optional hammer available. Made in U.S.A.