Fig. 24 Major League and RIF baseball cross sections. Top: The RIF balls are filled with a solid polyurethane core of which the weight, liveliness, and hardness can be varied independently. Bottom: A major league baseball has a complex interior consisting of the central “pill”—a composite cork/rubber center—surrounded by two layers of rubber, one red, the other black. The first wrap around the pill is a four-ply gray wool winding. The second wrap is a three-ply white wool winding. The third wrap is a three-ply gray wool winding. The fourth and final wrap is a fine cotton string that's a finish winding. Both balls are covered with two figure eight shaped cowhide pieces that are double stitched (108 stitches) by hand using 10/5 red thread. It is extremely difficult to feel a difference between the two finished balls.