Ergonomist-approved 60° vertical design for natural wrist and thumb positioning. Multi-device connectivity supports up to 4 devices. Rechargeable battery provides up to 4 months of use per charge. 4D scroll wheel for vertical and horizontal scrolling. Optical sensor with four DPI levels from 400 to 1600. 9 customizable buttons. Patented push-button trackball ejection for easy cleaning. 3-year limited warranty.