kensington MC K64325 Optical Expert Mouse� Wired Trackball Retail

TrackballWorks^TM lets you customize all 4 buttons, set cursor speed
DiamondEye^TM optical tracking technology for premium cursor control and accuracy
Award-winning Scroll Ring lets you scan up and down pages with ease
Large 55mm ball is designed as a perfect sphere to provide exceptional precision
Detachable wrist rest supports hand and wrist for ergonomic comfort
Reliable wired USB connection