Ergonomic Design, Removable Trackball, 9 Programmable Buttons, Connect up to Three Computers, 18-Month Battery Life. Work or play in comfort with the Pro Fit Ergo Vertical Wireless Trackball Mouse from Kensington. This mouse features a unique 60掳 tilt angle to provide an ergonomic form factor which promotes proper wrist arm and shoulder support ideal for prolonged computer use. The Pro Fit Ergo's design is similar to traditional mice which makes transitioning to this configuration easy. The trackball provides accurate and smooth cursor control that can be adjusted with an integrated DPI button located at the bottom of the mouse. Flexible wireless connection options allow stable connectivity giving you control for up to three computers at a time. Nine buttons can be programmed to fit a variety of tasks with the free KensingtonWorks software giving you the ability to fine-tune various aspects your mouse. The Pro Fit Ergo gains a lifespan up to 18 months off two AA batteries and is easy to clean with a dedicated trackball eject button.