Excellent Item! The 25mm model fit my Mossberg 500 SPX perfectly and allowed me to mount a SureFire X300 Ultra Weapon Light securely below the barrel. The mount has a "jackscrew hole" to crank the mount open slightly using one of the provided 8-32 screws. Spreading the mount slightly in this manner allows it to be carefully positioned, radially, on the magazine tube before final tightening, WITHOUT marring the tubes finish by wrestling the snug fitting mount around into the desired position. Best $55.00 solution I've found to mount a light or LASER!!!!