The AR9-FC-MB is a linear compensator (flash can) for 9mm AR-9 builds. It redirects muzzle blast, concussion, and sound forward and downrange, which improves shooter comfort - especially noticeable on short AR-9 pistols and SBRs. Features: Redirects blast, concussion, and sound forward, away from the shooter Reduces felt concussion at the firing line on short barrels Built for 9mm AR-9 platforms This is a linear comp / flash can, not a recoil-reducing muzzle brake. 9mm AR threads are commonly 1/2x36, but some 9mm devices use 1/2x28 - confirm your barrel's thread pitch before ordering.