Markwort Weighted 9" Leather Covered Training Baseball (3 OZ) : Build your arm strength with Markwort training weighted baseballs. As you train gradually increase the weight of the ball as you build strength in your throwing arm. Color coded cover indicates the ball weight. Weighted baseballs are 9 inch circumference with varying weights. Leather cover, white stitching. Weighted core. Size of regulation baseballs are 9 and 5 oz.