The Kensington Orbit Trackball with Scroll Ring, model K72337US, is a track ball designed for use by individuals with grasping disabilities or limited dexterity. This track ball enables the user to move the cursor with a fingertip. The track ball is encircled by a scroll ring that allows click-free scrolling through web pages and documents. The unit has an ambidextrous design that is equally accessible to left- or right-handed users. It connects to a computer through a USB port. COMPATIBILTY: For use on IBM and compatible personal computers (PC) or Macintosh computers. SYSTEM REQUIREMENTS: PCs require Windows XP or Vista operating system. Mac requires Mac OS X operating system. WARRANTY: 5 years.