The Clearly Superior Technologies PC Trac Ergonomic Trackball allows young and old alike to work in comfort for hours at a time. The large, high density ball, and the shape of the Clearly Superior Trackball case, act as a natural hand rest that mirrors the contour of the hand. Combined with the special "Ambidextrous" feature, the CSTrac accommodates both right and left handed users (without changing system settings) and hands of all sizes. No need to move your arm or rotate your wrist from side to side. You"ll enjoy this trackball"s ability to dynamically accelerate across the screen as you turn the ball faster. This trackball mouse will enhance any system.