Overview of Major League standards for baseballs: Must be a sphere Must weigh between 5.00 and 5.25 ounces. Must measure between 9.00 and 9.25 inches in circumference. What is a baseball made of?   Let’s start at the center of the ball and work our way out. The core of a professional baseball is called “the pill.” The pill is a small round object, smaller than a golf ball, that has a rubber outer casing and a cork center.     Around the core, are several layers of tightly wrapped yarn and twine. Each layer of yarn and twine …