EGW Mossberg ATR/4X4 Long Action 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. Lightweight Tactical mounts have a milled center channel for weight reduction. Full-width cross-slots are gauged to MIL-STD 1913 specs to +/-.002". Machined from ultra-rigid, extruded 6061 T6 aluminum. Includes socket head TorxA(R) screws and wrench. EGW Mfg: Egw