Upgrade to the Logitech Optical Wheel Mouse Enterprise Edition and never look back.  You'll be impressed with the state of the art optical sensors that provide ultra-smooth tracking on almost any suface.  Forget about cleaning or maintaining this mouse, because it's simply not necessary thanks to the optical feature.  Optical mice also outlast traditional ball-based mice because there's no moving parts in them, and the Enterprise Edition is very easy to work with since it easily plugs into a PS/2 or USB port.  Left or right-handed users can use this mouse and once you start clicking with the Enterprise Edition you'll never want to stop. This pack comes with 5 mice, all colored black.