Designed specifically to fit their AZ-EQ6 mounts, the Sky-Watcher 11-Pound Counterweight is critical to properly balance your optical tube assembly (OTA) on the mount, so it can move smoothly and track accurately without unwanted vibration or putting additional wear and tear on the motors. This heavy counterweight can be used with larger telescopes like catadioptrics or intricate imaging systems with focal reducers, filter wheels, large cameras, and guide scopes. The thumbscrew allows you set the counterweight anywhere along the length of the counterweight shaft for precise balancing.