Picatinny rail mount built for Mossberg 500 and 590 Series or equivalent shotguns. Allows mounting of Picatinny or Weaver standard scopes, red dots, magnifiers, or other optics. Installs via included set screws into the Mossberg factory mounting holes. Crafted from lightweight aluminum, 5.4 inches in length and 1.4 ounces in weight. Note: pre-1997 Mossberg shotguns may have different sized factory mounting holes; the rail fits but requires 6x48 TPI screws (available at hardware stores).