Counterweight shaft with safety screw for following mounts: Strain Wave AZ/EQ mount HAE series SkyGuider Pro SkyHunter SkyTracked Pro (CW package) It also can be used as an extension bar. Diameter: 20 mm (0.79 in.) Length: 200 mm (7.875 in.) Thread: 3/8"-16 (both ends) Weight: 1 lb Safety Screw: included