Standard 14mm- DETAILS: The Ferfrans CQB Modular Muzzle Brake System is based around the Muzzle Brake Mount (MBM). When the projectile exits the barrel, the MBM redirects the expanding gases in the opposite direction of the muzzle climb, helping you stay on target and reducing the felt recoil. The Ferfrans brake goes above and beyond with the inclusion of the the Concussion Reduction Device (CRD), a perforated cylinder that fits around the brake itself to contain the noise and gases. This mitigates the biggest downside of using a brake, which is the shock waves and loud report projected to the sides by other brakes. The CRD is particularly useful on the shooting range, where the concussive forces from other brakes are quite an annoyance and even a safety hazard to adjacent shooters. The CRD can be taken on and off at will using an integral quick attach/detach mechanism. Tags - please ignore this: Eotech 558 XPS XPS-2 EXPS 3x Magnifier G33 flip to side combo black tan 4x zoom trijicon mr 4x acog PEQ-15 green red laser lumen lumens peq La-5c peg15 block | Block II block 1 block 2 suppressor silencer noveske amplifier sniper unity pig brig Ferans magpul mbus rcnc 416 Tracer Silencer SR25 keymod mlok m-lok tr str prs vltor hanguard