This is our signature carrier assembly. Added surface area in the front of the carrier gives a tighter fit when the bolt is in battery for more consistent lock up. This unit is complete with gas key, bolt, cam pin, and firing pin ready to install in your rifle. AR15 weighs 11.3 ounces and the M16 weighs 11.4 ouncesWhat makes Young Manufacturing AR15 bolts and bolt carriers so accurate? Check our “What makes our Bolt Carriers Better?” on our home page.