The reason is that the unique & patented shape of the Hand Shoe Mouse fully supports your hand in the best relaxed position & prevents gripping & pinching, what you do when you use a standard mouse. The Hand Shoe Mouse was developed with all complaints in mind. Support of your hand & fingers prevents gripping & pinching & your arm is supported at the ideal angle of 25-30 degrees which makes sure your forearm is completely relaxed. Instead of over-using your hand & wrist, your arm will most of the time let the optical Hand Shoe Mouse float without any effort. The shape allows for the hand to continuously rest on the mouse body in a relaxed fashion, so there is no skin contact between your hand & the desk. As a result there is no skin irritation as caused by excessive rubbing when moving a conventional mouse. The buttons of this ergonomic mouse are positioned in line with the fingers. Only minor pressure is required to click the buttons. The thumb rest of the Hand Shoe Mouse allows for a relaxed position & prevents excessive thumb action which can be harmful.