Scientific ergonomic design encourages healthy neutral "handshake" wrist and arm positions for smoother movement and less overall strain. 800 / 1200 / 1600 DPI Resolution Optical Tracking Technology provides more sensitivity than standard optical mice for smooth and precise tracking on a wide range of surfaces. Added next/previous buttons provide convenience when webpage browsing; the superior choice for internet surfers, gamers and people who work at length at the computer.