... can reach over 12,000 RPM.TheoryLike gyroscopes.centrifugal force and inertia are applied.Function:1.Perfect exercise gadget for ... in fingers, wrists, hands, forearms, biceps, triceps, ligament and shoulders3. Great benefit and avoid the ligament injuries who are the typists, musicians ... of the ball. That can prevent the ball from sliding down to the ground, and the feeling of grasping is also better.3 ...