EGW Mossberg 500, 590, 835, 930, 935 Post-1997 Heavy Duty Scope Bases. Add the versatility of a one-piece Picatinny scope rail to your shotgun with no drilling or tapping. Precision machined from extruded aluminum with Picatinny slot-and-rail spacing that allows fast and simple changes to eye relief, plus great flexibility in scope choice. Drilled to fit the factory scope mount holes on the gun's receiver. Accepts Picatinny or Weaver scope rings. Heavy Duty mounts are .100" lower than the Lightweight mounts to minimize weight and keep your optic closer to the barrel centerline for improved accuracy. Full-width cross-slots are gauged to MIL-STD 1913 specs to +/-.002". M Mfg: Egw