The M6 is designed for use on a Glock mounting rail. Some weapons employ the dimensions and specifications of the Glock mounting rail, while other weapons conform to the MIL-STD-1913 (Picatinny). The difference in the tolerances will affect the fit of the M6 on a weapon-mounting rail. It is important to maintain the original configuration of the M6. The mounting should not be modified, as that could affect the reliability of the laser aiming system.

In-house testing has shown that affixing the light to the mounting rail and allowing it to set up for a few days can allow the mounting to conform more suitably. Additionally, try to fit the light onto the mounting rail without the locking bar. If the light fits better, the locking bar may need some adjustment to help improve the fit. The top of the locking bar may have a tiny amount of flash on it from the molding process. Lightly scraping this material away with a sharp knife or file should help the fit. Try not to be too aggressive at first. You may have to repeat the process several times to get a better fit. It is not necessary to remove much of the material.