Made of high-quality aviation aluminum alloy and a black hard coat anodized finish, it is sturdy and durable. Convert 11 mm Dovetail to 21mm Picatinny Rail - 7.88 inches length at the base, the Picatinny rail extends 10.24 inches. The top 21mm Picatinny rail allows for the mounting to fit most Weaver and Picatinny rail's standard scopes, or other accessories, allowing for more flexible optics placement. The 11mm dovetail mounts mounting is for flat tops dovetails and will work with round tops The quick-release design provides firm and secure mounting, The Rail adaptor installs easily via dovetail mount and one vertical stop pin, and an attached Allen wrench can help you to tight and stable with no shaking.