The M4SD Flash Comp optimally combines the functions of three traditionally separate classes of devices- Muzzle Brakes, Tactical Compensators, and Flash Suppressors. The M4SD II Flash Comp achieved a perfect 5 out of 5 in National Tactical Officers Association testing to achieve the rare, coveted, NTOA Gold seal of approval granted to devices which achieve perfect evaluations. Compatible with the M4SD series GATE-LOK suppressor interface the Flash Comp provides a sacrificial baffle to increase the service life of your silencer. It is also pre drilled, and 2.25" length for 14.5 to 16" permanently attached, Non-SBR, M4 carbine builds. For optimal flash reduction we recommend Mfg: Griffin Armament