Forward Controls Design 3P15 - 5.56 1/2x28

3P15 is shorter and smaller in diameter than many suppressor mounts/flash suppressors, these dimensions are defined by compatibility with Plan B and Atlas adapters. Our design philosophy regarding suppressor mounts is that in addition to their ability to mount the suppressors for which they're designed, they should be good flash suppressors, compensators, brake, etc. in their own right. The internal grooves serve to improve gas expansion and cooling, but by themselves, they're not sufficient to make the device a better flash suppressor.  Distance between each prong, the shape of the opening, the bore size and the length of the prongs are all factors.