Gemtech GVAC, Complete Upper Reciver Group, 223 Remington/556 NATO, 16.1 Barrel, 1:8 Twist, Gemtech ETM Flash Hider, Pinned Low Pro GVAC Gas Block, Mid Length Gas System, Anodized Finish, Black, MLOK Handguard, Fits AR-15, Includes Bolt Carrier Group 13833 Introducing the new GVAC system from Gemtech. Significantly reduce the amount of gas blowback you'll experience when shooting suppressed with its patented design. The re-imagined barrel profile" enhanced bolt carrier profile" enhanced bolt carrier group" and ETM muzzle device maximize performance so nothing holds you back. Redefine suppressed shooting with the GVAC system.