Ergonomist-Approved Design - Promotes proper wrist, arm, and shoulder alignment to maximize comfort and minimize potential strains. Easy to Use - Reduces learning curve when transitioning from a mouse to a trackball. Premium Precision & Speed - Provides more accurate and smooth cursor control, and allows you to easily switch between DPI settings for different cursor speed control. Flexible Wireless Connection Options - Allows stable connectivity for up to three computers. Plug & Play or Customize - Use the default settings or download KensingtonWorks software to set pointer and scrolling options and professionally customize nine buttons to tackle common tasks with one touch. Unique Easy-to-Clean Design - Features a button to eject the trackball for easy cleaning. Long Battery Life - Works for up to 18 months on two AA batteries (included). The battery indicator light eliminates surprises. Battery life may vary based on usage.