Description for 64325 EXPERT MOUSE USB PS/2 OP 4 BTN SCROLL RING: The best trackball ever made has just gotten better. Designed for PCs and Mac's, the new Expert Mouse employs Kensington's Diamond Eye optical technology for smooth, precise cursor movement. Surrounding the ball, Kensington has a brand new implementation of its award winning Scroll Ring that puts scrolling right at your fingertips. More comfortable than ever, the Expert Mouse even comes with a soft new wrist rest-right in the box! You get all of these great new features along with the same, large ball, exceptional control, and ease-of-use that has set the industry standard for more than 15 years.