Symmtrical Optical Trackball with medium sized ball and two mouse buttons

FEATURES- Orbit Optical- Metallic Black color
       2-button Optical Trackball
       Exceptional comfort with precise optical tracking.
       Optical laser precision guarantees accurate tracking, even if
        there's dust on the trackball; no regular cleaning required.
       Compact design in a comfortable fit for left or right hand; more
        comfortable than a mouse.
       Saves desk space - stays in one place, needs no mouse pad.
                                                                           
CONNECTOR- USB with PS/2 adapter                                           
REQUIRES- Mac  - USB port, OS 8.1 or later                                 
          PC   - Windows  98, Me, 2000, or XP with USB port                
          PC   - Windows  95, 98, Me, NT, 2000, or XP with PS/2 compatible 
                  mouse port.                                              
SIZE - 5.0"w x 1.5"h x 5.625"l                                             
 www.kensington.com