Kensington Expert Mouse Wired Trackball

DiamondEye Optical Tracking
Movement detection technology provides smooth, precise cursor control so you can get where you want on the screen quickly with less hand movement, improving productivity and efficiency.
Scroll Ring and Large Ball
Spin the dial to move up and down web pages or documents with complete ease while the grey ball has been specially designed with an absolute spherical, hard surface for precise tracking and control.
Ambidextrous Design
Works equally well for both right-handed and left-handed users to get the most out of their trackball.