... Item No.: 868NC Product name:Wrist ball with LED and COUNTER Description:Shell material: A grade PCRoller ... the device, it is powered by rotating the wrist, and the speed of rotation can reach over ... fingers, wrists,hands,forearms,biceps,triceps,ligament and shoulders.-Great benefit for musicians,guitarists, pianists ... .-Do not use this product persons who with heart conditions of any description.-It is ...