The BIGtrack has a 3 inch trackball which makes it the largest trackball available. The large ball requires less fine motor control than a standard trackball and it is ruggedly built. It has a left and a right mouse click button located behind the trackball to avoid unwanted mouse clicks. The BIGtrack also allows for 2nd Mouse Connection both the BIGtrack and a second mouse can be connected allowing simultaneous participation. The bright large 3" trackball helps to make mouse movements easy and accurate. While the oversized buttons make mouse clicks simple for those with poor motor control. For even more access the BIGtrack is available in a switch adapted version. The switch adapted BIGtrack comes with two standard 1/8" plugs for two switches. Its left and right mouse clicks have been adapted so that you can use a switch for activation. (Switches sold separately) Get the BIGtrack Switch Adapted with PointSmart for a total assistive technology solution. The BIGtrack is easy to install and works on any Windows or Macintosh computer that has a USB or PS/2 port. Just plug and play.