Kensington Expert Mouse Wireless Optical Trackball for PC or Mac 64329 Kensington Edge: Award-winning Scroll Ring puts trackball scrolling at your fingertips. Quick RF Wireless connectivity provides wireless speeds as fast as a cabled mouse or trackball DiamondEye Optical tracking for unrivaled precision and accuracy Detachable wrist rest comfortably cradles hand for increased productivity, sleek black and silver design matches latest PC styles Largest ball of any of the mainstream, consumer trackballs; Windows or Mac compatible; USB/PS2