Conditioning with weighted balls has been referred to as Overload Training. Many players agree that training with weighted balls can improve their velocity when playing with a regulation game ball. As with other types of weight training programs they strength his or her arm by training with progressively heavier balls. Each set contains 1 each: 7 oz, 8 oz., 9 oz., 10 oz., 11 oz. & 12 oz. baseballs. (TK)