Scroll Ring and Medium Ball - Spin the dial to move up and down web pages or documents with complete ease. The blue 40 mm ball has been specially designed with an absolute spherical, hard surface for precise tracking and control KensingtonWorks Customization - Free downloadable software provides an even more personalized experience, giving you the ability to assign a wide variety of program functions to each of the 2 buttons, as well as adjusting cursor and scrolling speeds