Reliable optical technology combined with an innovative scroll wheel that acts as a third button sets Logitech's 904353-0403 Trackman Wheel Optical apart from ordinary trackball mice. Patented optical technology provides superior precision, reduced wear, and smooth motion, and eliminates the need for regular cleaning. The scroll wheel provides easy scrolling and the added convenience of an extra mouse button, enabling you to jump easily to your favorite Web sites. The ball is ideally positioned for thumb operation, and the comfortable shape of the mouse allows for strain-free extended use. Its smaller size also saves desk space, reduces hand and wrist movement, and plugs very easily into your system's USB or PS/2 port. Compatible with both Windows and Macintosh systems.