... axle2.no any battery, powered by rotating the wrist3.Perfect exercise gadget for sports4. strong the muscle system of arm ... tennis, golf, basket-ball, table tennis, badminton, bowling, rowing, rock-climbing ,basketball, motocross, mountain climbing ,etc. Function: exercise the human wrist as ... considerably and is great fun at the same time. You exercise muscles in your arms, your wrists, the grip of ...