Contour optical mouse specially designed arch fills the hollow of your palm and allows you to rest your hand on top of the mouse. This arch promotes straight alignment of your hand and wrist bones and slightly elevates your wrist off of the working surface. This helps to break the harmful habit of resting your wrist on the desk or mouse pad and pivoting the mouse from side to side. That pivoting can cause pain and discomfort as the forearm bones (radius and ulna) twist in directions not easily tolerated by human physiology.