Avoids forearm twisting for comfort and good healthThe patented shape supports your hand in an upright neutral posture that generally avoids forearm twisting. Many users. including medical doctors. ergonomists and physical therapists. said the Evoluent VerticalMouse provides superior comfort and even relieved their wrist pain.Comfortable and easy to useThe shape is thoughtfully sculpted for uncompromised comfort and easy-to-reach programmable buttons. No finger contortions are needed to operate the buttons.Adjustable optical sensorPointer speed controls on the side allow convenient adjustment without even releasing your grip from the mouse.Improved thumb restThe thumb rest has been reshaped to provide even more comfort over earlier versions.Pointer speed indicatorsTop mounted LEDs show through the chrome thumb rest to indicate selected pointer speed including extra low (XL). low (LO). MD (medium).