This AR-15 Complete 5.56 Upper has a 16" light-weight barrel with a parkerized finish, and features a 1:7 twist, with a carbine length gas system. It includes the new 15" MLOK rail, a M4 flat-top forged upper receiver, a Bolt Carrier Group, Flash Hider, and a rear charging handle. This 5.56 upper is compatible with any mil-spec AR-15 lower.