I forgot to say when my left hand became chronically painful due to using a mouse, I got a rolling ball device, based on advice of Mudcatters. It has helped me tremendously, esp. my thumb. I've learned to click with my other fingers and the ball shape, plus the unit it sits in, fit the natural lines of my hand, so there is no extension of the thimb to the side, a stressful contortion, plus my other fingers have gained in strength. FWIW...kat