Features:<br> Fit for 21mm weaver-picatinny rail mount dovetail rail mount. With hex-key,accurate made.<br> Small size allows for convenient storage and transport.<br> Eliminate canting and improve long-range accuracy with these bolt on scope mounted spirit levels.<br> High quality materials, exquisite technology, fine workmanship, better impact / more durable.<br> These bolts are mounted on the horizontal-surface of the oscilloscope installation to eliminate tilt and misalignment.<br> <br> Specifications:<br> Material:Aluminum Alloy<br> Size:As Picture Shown<br> Type: Cylindrical level(Without wrench)<br> Compatible with 20mm rail<br> Color: black shells + green-liquid<br> <br> Note:<br> 1.Please allow 1-2cm errors due to manual measurement, make sure that you do not mind before you order.<br> 2.Due to the difference between different monitors, the picture may not reflect the actual color of the item.<br> Thanks for your understandings.<br> <br> Package includes:<br> 1x Tactical Bubble Level