Macally is proud to introduce one of the industry's first optical sensor Trackball. This optical sensor Trackball eliminates the mechanical structures associated the conventional Trackball. To enhance the optical technology Macally has added stainless steel ball bearings to give the users more precise and accurate pointing. In addition, a new tracking ball - Glitter Ball was developed. The result of the new features the user will enjoy precise, effortless cursor control and visual effects associated with the Glitter Ball. Macally's optical sensor Trackball will be the highest quality Trackball you can find on the market.??This trackball is designed for G3/G4, iMac or PowerBook with built-in USB port or any PowerPC with 3rd party USB adapter installed.