AR-15 Complete Side Charging Upper has a 7.5" M4 Contour Parkerized barrel and features a 1:7 Twist Rate, a Pistol length gas system. it includes a 7 5/16" MLOK Rail, an M4 flat-top forged upper receiver, a Bolt Carrier Group, a Flash Hider, and a Gen 2 Side Charging Handle (patent pending). It is chambered in 5.56 NATO.