The Q Rearend XL Muzzle Brake is a Quickie Fast-Attach muzzle brake built specifically for 8.6 BLK and designed to run seamlessly with Q's SHORT CHOP and PORQ CHOP silencers. Scaled up from the original Rear End to handle the thump and authority of 8.6 cartridge.Q Rearend XL Muzzle Brake5/8x24 threading for 338 caliber compatibilityQuickie Fast-Attach system for rapid silencer mountingCompatible with Q SHORT CHOP and PORQ CHOP silencersDesigned for barrels with 90-degree shouldersWrench flats for easier installationTapered mount system for secure attachmentPerfect for 8.6 BLK builds requiring fast silencer attachment and detachment offering the same proven DNA as the original Rear End with enhanced capability for larger calibers.