Make Arm Great . Strengthen fingers, wrists, hands, forearms, shoulders and bicep etc., and also be beneficial in promoting co-ordination and blood circulation. Automatic start design, need to push the core in the direction of the arrow, start by the internal spring, very easy and convenient. When it rotates, the cool colored lights inside wheel light up. It can kill time and add fun while restoring muscle soreness. Small, compact and transportable, you can take anywhere. Simple to start with a pull-string.And the ball with flashing LED ，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.