A baseball has three basic components. These consist of a cushioned cork and rubber casing at its core, wool and poly/cotton yarn surrounding the core, and a cowhide cover over the exterior of the ball.
The core of a baseball is made of cork and rubber, and measures 3/16-inch in diameter. It is encased in two layers of rubber for added strength. The core is wound in four layers of wool and yarn, each with varying levels of length, thickness and strength. Wool is primarily used to wind baseballs due to its ability to be compressed repeatedly, while quickly regaining its original shape.
The first set of windings is made of gray woolen yarn and is the thickest layer. The second layer is a three-ply white woolen yarn. The third layer is a three-ply gray woolen yarn, and the fourth layer is a white poly/cotton finishing yarn.
The cover of a baseball is made from cowhide. Midwest Holsteins are preferred because they yield a cleaner and smoother grain that holds up better than hides from cattle in other parts of the U.S. Official baseballs are white and sewn together with 88 inches of waxed red thread. Once the ball has been manufactured, it undergoes a series of tests to measure for size and strength before being approved for use.