The mouse is still the most-used computer and laptop accessory, so a good, ergonomic mouse is essential. The Evoluent 4 is a vertical mouse, which you hold in a handshake position. With this posture there is less lateral wrist-bending and forearm rotation. Using the wrong mouse can lead to pain and discomfort in the shoulders, forearms and hands.... With a vertical mouse you can prevent many of these problems.