KENSINGTON Orbit Trackball Wired Ambidextrous Optical Mouse  (USB 2.0, Grey)

Optical tracking technology for superior cursor control and accuracy, medium 40mm ball is designed as a perfect sphere to provide exceptional precision. Compact footprint takes up less desk space than you’d need to operate a mouse, ambidextrous design works equally well for both right-handed and left-handed users. Plug and Play installation via wired USB connection. TrackballWorks software lets you customize the 2 buttons, adjust cursor speed. Compatible with Windows 8.