... powered by rotating the wrist. The faster we rotate the ball, the stronger the dynamic and torsion is produced. The speed ... sports like golf, tennis, squash, cricket, badminton, baseball, bowling, basket-ball,, motocross, mountain climbing.2. Increases strength in fingers, wrists, hands ... plastic material is especially durable4) The axle is made of steel, not iron. It is not easy to be broken.