The VerticalMouse D (Right handed small sized mouse) by Evoluent helps avoids forearm twisting for comfort and good health NEW grooved buttons provides additional grip and precision when mousing The shape is thoughtfully sculpted for uncompromising comfort and easy-to-reach programmable buttons No finger contortions are needed to operate the buttons The thumb rest has been reshaped to provide even more comfort over earlier versions Features two thumb buttons which provides greatly extended functionality when used with the included driver An extra wide lip along the bottom edge prevents the last finger from rubbing the desk Pointer speed controls on the side allow convenient adjustment without even releasing your grip from the mouse Top mounted LEDs show through the thumb rest to indicate selected pointer speed including extra low (XL) low (LO) MD (medium) to high (HI) Basic functionality in OS X or newer without a driver Linux - Basic functionality without a driver