11mm (3/8") Dovetail to Weaver Adapter Insert into Weaver or Picatinny rings so they'll fit the smaller 3/8" or 11mm rails and dovetails often found on airguns and rimfire guns 1" long .93" wide .24" high .18 oz 2 pieces If your air gun or rimfire gun has a scope dovetail that measures either 11mm or 3/8" (approx. 9.5mm), you can use this lightweight aluminum adapter to attach your Weaver and Picatinny rings or mount to your smaller 11mm and 3/8" dovetails.