HP - Mouse - optical- 3 buttons

Optical tracking - reduce sticking and constant cleaning with optical tracking - a system that works through light with less moving parts for greater durability than ball-based mice
Users benefit from a smooth, contoured shape that fits both hands - and a wheel that functions as a third button
The optical sensor within the HP USB optical scroll mouse employs a scan rate of 800dpi and enables crisp motion without a mouse pad, ball or roller
Utilizing the latest optical sensing technology, the HP USB optical scroll mouse records precise motion over a variety of surfaces without a mouse pad.