Features: Quickly and easily level your optics in the outdoor, at ranges, or at home. Convenient storage and transport. Great for long range shooting. Provides a precise level. Compatible with 20mm and 11mm rail systems. Installs quickly and securely onto rail mounts. Use this bubble level to ensure your rifle is level when aiming at targets. Mounts quickly and easily to the rifle scope tube. Specifications: Materials: Aluminum alloys Clamping Size: 20mm (0.79 inch) / 11mm (0.43 inch) Package Includes: 1 pc Scope Bubble Level Note: Please allow 1-2 cm errors due to manual measurement. The picture may not reflect the actual color due to differences in monitor settings. The item's color may be slightly different from the images due to lighting and screen settings. Slight dimensional differences may occur due to manual measurement.