Champro CSB7S Weighted Training Softball Set (Incudes 9oz, 10oz, 11oz, 12oz)Set of 4 training softballs Full grain leather covers Raised seams Training program included The Concept: Conditioning with weighted balls ahas 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 the strength of his or her arm by training with progressively heavier balls. Each set contains 1 each: 9 oz