The PR-MO Mossberg 500 Rail System offers a superior mounting solution for your Mossberg accessories. Advantages: Enables Three Picatinny Rails Mount Picatinny Based Accessories on Your Shotgun State-of-the-Art Ergonomic Design Durable, Hardwearing & Lightweight construction Quick & Easy Installation No Gunsmith Required Provides Appropriate Thermal Insulation Constructed from Reinforced Polymer Composite Compatibility: 12 Gauge, MossbergA(R) 500A(R), 590A(R), ShockwaveA(R) and MaverickA(R) 88A(R) ( MaverickA(R) 88A(R) requiters purchasing separately a MossbergA(R) 500A(R) 7-3/4" Action Slide). Will not fit the Mag-Fed versions.