AR-15 Low Concussion Muzzle Brake 1/2x28 Pitch TPI Knurled -3 ports. The "Low Concussion" muzzle brake is designed with Compact design for CQB and Tactical Low Concussion to operators. Optimized linear baffles for maximum brake performance and low concussion. an aggressive profile and 6 short prongs for a unique look. It has a total of 3 ports to redirect pressure, resulting in less muzzle rise and overall recoil. Constructed of CNC machined 4150 steel and finished with Black Oxide.