This AR-STONER upper features a Mil-Spec bolt carrier group, parkerized finish, low profile gas block, and a M4 profile barrel. The A3 upper will attach to virtually any standard AR-15 lower receiver and comes complete with charging handle, forward assist, ejection port cover, muzzle brake, bolt and bolt carrier assembly. Supplied without a rear sight, this upper is a great platform for a red dot sight or iron sights (both sold separately).Features:16" Parkerized 4150 Chrome Moly Vanadium BarrelM4 Contour Barrel15" MLOK RailRear Charging