Clamps on to a standard 3/8" and 11mm width airgun/.22 dovetail base rail to convert it to a Weaver/Picatinny base that can take weaver/picatinny base mounts instead.

Very handy if you want to take advantage of the many more types and styles of rifle scope mount that are available for this type of base e.g., the really excellent Leapers Twist lock and QD makes we stock.
 

• 22/Airgun Mount Base to Weaver/Picatinny Tactical Rail Adaptor
• Made from Aircraft Grade Aluminum Alloy with Matte Black Finish
• 9.9cm/ 3.9" Long Top Rail with 9 Slots and Middle V-cut
• Complete with One Vertical Stop Pin