Monstrum Tactical Low Profile Dovetail to Picatinny Rail Adaptor Dovetail to Picatinny rail adaptor for firearms equipped with 11mm or 3/8 inch dovetail standard rails Dovetail rails typically found on air rifles or certain model .22 rimfire rifles Picatinny rail allows for the mounting of Picatinny or Weaver standard scopes, red dots, magnifiers, or other optics Rail adaptor installs easily via dovetail mount and one vertical stop pin 2.8 inches at the base, the Picatinny rail extends 3.9 inches allowing for more flexible optics placement and eye relief