The primary purpose of the BoreLock mounting collar is to enable the user to continue using a flash hider or a muzzle brake that is already on the weapon. To be compatible with the BoreLock mounting collar and suppressors, the muzzle device needs to be under 22 mm in diameter and have a maximum length of 63 mm. NOTICE! With DUAL-S-BL, SL5i, SL6i and SL7i the maximal length of the combination is 52 mm.