cross section of a baseball

A baseball has a cork core, which is wrapped in layers of rubber, wound with yarn and covered with leather.

stitches

The sewing that joins the two parts of the cover; it traditionally uses red thread.

cover

Outer layer of the ball made up of two white pieces of leather joined by stitching.

cork ball

Small sphere of cork that forms the central part of the ball.

yarn ball

Yarn wound around the center of the ball.