The Markwort Weighted Ball comes with real seams and are a great training aid for pitchers and any players wishing to throw harder. As you train, gradually increase the weight of the ball as you increase the strength of the pitching and throwing arm. These balls work for players of all ages. The weighted balls can be purchased individually and in a 4 or 6 ball set. The 4 ball Weighted Set contains one 9 oz., one 10 oz., one 11 oz., and one 12 oz. softballs with a mesh drawstring bag. The 6 Ball Weighted Set includes a carry bag and comes with one softball of each of the following weights: 5 oz, 7 oz, 9 oz, 10 oz, 11 oz, and 12 oz.