If you have a Mossberg Model 500 with a drilled and tapped receiver, then you absolutely must have the UTG Pro Model 500 Shotgun Picatinny Rail Mount. The contoured bottom gives it a perfect fit and it has a low profile with see-thru design for use of the front bead sight. It is precision machined from aircraft grade aluminum with a matt black hard-coat anodized finish. It has a 5 1/2" length with 13 Picatinny rail slots for Dot Sights, Rear Sights, and flexible positioning of magnified optics for proper eye relief adjustment. Includes assembly screws and tools for simple and easy installation.