This AR-STONER AR-15 5.56mm Barrel is perfect for competition or plinking where reliability is imperative to a successful day. This M4 contour barrel is made from 4140 Chrome Moly Vanadium Steel and uses a 1 in 7" Twist. Additional features include a mid-length gas port, M4 feed ramps and 1/2"-28 threaded muzzle. Barrel extension and locator pin are both included and factory installed.