This is the discontinued but still popular Ergo Vertical Wireless Trackball Mouse. The buttons have been changed to silent ones. This specification prevents clicks from echoing in a quiet office, reducing stress. It has been disassembled and cleaned, and the scroll button functions without any malfunctions. Product Description: / / / / / / / / / / / / / / / / / / / / / Comfort in the palm of your hand. The Kensington Pro Fit Ergo Vertical Wireless Trackball, with comfort and operability recognized by ergonomists. The 60-degree tilt allows you to operate your wrist and forearm in a stress-free position when using the mouse. Because it's a trackball similar to using a mouse, it's easy to transition from a mouse, and it has 9 programmable buttons. The 60-degree tilt, like shaking hands, allows you to operate your wrist and forearm in a stress-free position when using the mouse, and allows for thumb control. Ergonomist-approved design for comfortable operation all day long. It has the same left-click, right-click, and scroll wheel operations as a conventional mouse, with the addition of thumb operation, making it easy to use and simple to operate. High-precision optical tracking sensor, 34mm trackball controlled by thumb operation, and a 3-stage DPI switch enable smooth cursor control, allowing for both delicate and speed control. Three connection options to the device - 2.4GHz nano receiver, and two types of Bluetooth connections are possible. Plug and play for immediate use, or use KensingtonWorks to control pointer and scroll speed, and assign 9 function buttons. The unique and easy-to-clean design allows you to quickly remove the trackball and remove dirt, bacteria, and dust. Two AA batteries (included) provide typically 18 months of use. With a battery indicator to prevent sudden malfunctions. Connection type: Wireless (Bluetooth) Power supply: Battery powered