To prevent Repetited Strain Injury (RSI), a painful, numb feeling in your arm(s), wrist(s) and/or hands(s) during and after working with a computer for a prolonged period of time, it is important to have an ergonomical posture while working. A wrist rest for use with your mouse prevents flexion of the wrist, thus reducing the risk of getting a so called 'mouse wrist', RSI in the wrist. A wrist rest for use with a keyboard is not intended for resting your wrist on while working. Use it only for during breaks, to prevent your wrists from unncessary strain.