Franklin Sports MLB 3 Pack Training Balls - 12.5 oz, 17.5 oz, 22.5 oz Set includes 3 training balls; Sizes 12.5 oz, 17.5 oz, & 22.5 oz. Add strength and power to your swing through resistance training Provides the hitter with instant feedback Can be used for both Baseball and fast pitch Softball Promotes proper hip rotation and swing follow through