The Expert Mouse Wired Trackball is the ultimate productivity enhancer that makes working at the desk quicker, more accurate and extremely comfortable for your hand and wrist. Featuring DiamondEye technology, the trackball uses optical tracking to precisely follow small flecks embedded in the large 55mm ball to provide smooth, accurate cursor control. The four buttons are customizable using our highly intuitive KensingtonWorks software, while our award winning Scroll Ring lets you quickly scan up and down web pages and large documents. Add it all up and you get exceptional comfort and ease-of-use that has set the industry standard for more than 20 years.