The Adesso 2 Button Desktop Optical Trackball Mouse is ergonomically designed to make your daily computer use comfortable and stress-free. The trackball is ergonomically contoured to fit a user's palm comfortably and the unique side scrolling wheel eliminates the strain traditional mice cause your hand when scrolling. With its 800 DPI resolution the optical trackball provides superior accuracy and smooth motion, requiring minimal hand movement or space. This mouse trackball is also easy to maintain just push trackball outward from back, clean and push back in place.