Features OOTDTY Material: The rail barrel tube clamp is suitable for sight and flashlight , solid aluminum alloy structure, hard black anodized finish. Maximum barrel outer diameter: 21mm, easy to install (including tools), comes with a wrench, right on your barrel. Very suitable for installing flashlights, torch sights, bipods and more. Easy to mount: Rail mount for mounting flashlights to rail equipped rifles or shotguns. Specifications: 10mm-21mm diameter, guide rail 20mm. Durable: Durable all-metal structure, light weight. Specification Material: Aluminum Alloy Size: approx.3.5x2cm/1.37x0.78in Color: As the picture shown Quantity: 1Set Note Please allow 0-1cm error due to manual measurement. pls make sure you do not mind before you bid. Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thank you! Package Contents 1 X for butterfly Pipe Clamp 1 X Wrench(other accessories demo in the picture is not included.)