This BCA AR-15 complete .223 Wylde rifle length upper has a 20" straight fluted heavy barrel with a stainless finish, and features a 1:8 twist rate, with a rifle length gas system. It includes a 15 1/4" MLOK rail, an M4 flat-top billet upper receiver, a BCA bolt carrier group, a flash hider, and a rear charging handle. This .223 Wylde upper is compatible with any mil-spec AR-15 lower.