Columbia 300's Classic Vinyl wrist positioner is specially designed to help you throw a ball with precision, accuracy, and power. When set with the thumb on top of the ball, the Classic Vinyl wrist positioner produces the normal 11 o'clock 5 o'clock position, enabling the ball to swing out in a true pendulum. At the bottom of the pendulum swing, the positioner supports your wrist and lets the thumb release cleanly. Both back and front metal supports maximize wrist strength while allowing the ideal wrist angle for superb delivery.Product Type Bowling Accessories