Hewlett Packard HP - mouse PS/2

Optical tracking - Get precision movement with a tracking system that works through light for less moving parts and greater durability than ball-based mice. The optical sensor within the HP PS/2 2-Button Optical Scroll Mouse employs a resolution of approximately 800dpi. Left-handed or right-handed users can enjoy a contoured shape that suits either preference, with a wheel that also functions as a third button.