The Goldtouch Semi-Vertical Mouse was created with an optimal slope of 66 degrees for the user who wants a mouse that is midway between a traditional ergonomic mouse and vertical mouse. Unlike fully vertical mice, you'll have the power of gravity on your side when it comes to clicking, so you won't have to use as much movement between the thumb and fingers (which in turn can require more pinching of your muscles and nerves).
Sizing:Using a ruler or tape measure, measure the distance from the crease in your wrist to the tip of your ring finger. Users with hands up to 19cm can comfortably use this mouse. If the attachment flange accessory is added, users with hands up to 20.3 can comfortably use this mouse. For larger hands, have a look at the Evoluent EVO4W mouse.