Gyroscope Wrist Ball Arm Exercise Strengthener LED Force Ball Wrist & Forearms With Speed Meter By Wincspace Strengthen fingers, wrists, hands, shoulders, forearms, triceps, ligament and biceps etc., beneficial grip strength trainer for golf, tennis, climbing, basketball etc.. Beneficial in promoting co-ordination and blood circulation, great for musicians, guitarists, pianists, drummers etc., and also be rehabilitates sore muscles and joint. Small, compact and transportable, you can take anywhere. Simple to start with a pull-string. This item is with speed counter and led light. Professional Digital LCD counter displays various vital workout information. Cool LED lights inside will light up while spinning, no battery needed, powered by rotating the wrist, 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. The faster you spin the harder your muscles work.