Features:- Simple to start with a pull-string.- The faster you spin the harder your muscles work.- Internal LED bulbs will light up when the ball is in motion.- Small, compact and transportable, you can take anywhere.- It is powered by rotating the wrist and the speed can reach up to 12.000RPM.- Rehabilitates sore muscles and joint, great for musicians, guitarists, pianists, drummers.- All you need do is to increase the speed by making a rotational wrist movement and to keep in sync with the spinning of the ball.- Strengthen fingers, wrists, hands, forearms, shoulders and bicep etc., and also be beneficial in promoting co-ordination and blood circulation.