The PR-MO Mossberg 500 Rail System offers a superior mounting solution for your Mossberg accessories. It is constructed of reinforced polymer with a state-of-the-art design and three Picatinny rails. This model has a black finish. It is compatible with 12 Gauge, Mossberg 500, 590, Shockwave and Maverick 88 ( Maverick 88 requires purchasing separately a Mossberg 500 7-3/4″ Action Slide). NOTE: This model will not fit the Mag-Fed versions nor will not fit the 14″ Barrel versions.