Strengthen fingers, wrists, hands, forearms, shoulders and bicep etc., and also be beneficial in promoting co-ordination and blood circulation. - Rehabilitates sore muscles and joint, great for musicians, guitarists, pianists, drummers. - Small, compact and transportable, you can take anywhere. Simple to start with a pull-string. - And the ball with flashing LEDAll 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. - The faster you spin the harder your muscles work. - Gyro ball/Force ball/power ball/magic balls get model sport now. - If you don’t know how to play it,can search video via youtube - It is fun and good for hands,wrist,shoulder, forearms,biceps and good as warm-up sport before you do climbing,golf,basketball etc Also if you use computer or play the piano for long time,you can play this ball every day for 15~20 minutes. - You will feel you hand won’t be so pain. - DO not drop the ball on hard surface at any time,the heavy rotor will damage. - DO not touch the ball rotor when it is spinning at high speeds,it will burn.