For those that don't like moving the mouse across the desk or are a bit limited for space the Orbit Trackball alleviates that problem. The mouse stays where it is and you control the cursor by moving the Trackball. It's a bit like an upside down mouse. Control your cursor with a simple touch of the finger. The highly accurate Orbit? Optical is as easy to use as a regular mouse, but it stays in one place saving you valuable desk space. The precise optical tracking mechanism is also resistant to dust, reducing the need for regular trackball cleaning. The Orbit Trackball is bigger than your normal mouse, this means the Trackball is easy to move and direct with precision. DiamondEye optical technology for precise tracking and cursor control The comfort of a mouse and the fingertip control of a trackball Uses less arm movement and desk space than a conventional mouse USB and PS/2 connectivity for greater compatibility