The Complete Guide to Baseballs

Learn how the anatomy of your baseball impacts its performance on the field.

It used to be made of shoe rubber and fish eyes and lemon peels.

Today, things are different. Now it’s cork, wool and alum leather, give or take a few other ingredients. The modern baseball, with its signature white surface and figure-eight stitching, is as much of an icon as the game itself. And the anatomy of your baseball plays an important role in its performance on the field.


Long-lasting leather covers are the traditional choice for many baseball players. They offer a secure grip, consistent play and durability over the long haul.

Newer, synthetic covers are less expensive — and ones crafted with top-grade cork cores may perform just as well as traditional leather balls. Many synthetic covers also resist dirt and maintain color better than leather, so they’re great for a muddy practice field.

Baseball COVER


The stitching on a baseball typically falls into three categories — raised, rolled or flat.

Beginners may play with a raised-seam baseball. Elevated from the surface of the ball, these seams “grip” the air for easier control. Major League Baseball uses rolled seams, which create less air friction than their raised counterparts.

As the name suggests, flat-seam baseballs lay flat against the surface of the ball, making them more difficult to grip and control. They are great for use in pitching machines.


So what’s inside your baseball? Most high-grade baseballs feature a grape-size, rubber-covered cork core, wrapped with thick layers of wool yarn, and then layered with a cover.

Major League Baseball regulation balls are between 9 and 9 ¼ inches in circumference and weigh between five and 5 ¼ ounces.

baseball core


In the past, there were “safety balls.” Today, manufacturers offer specialized “Reduced Injury Factor” balls for youth players. These balls have a softer, typically polyurethane core, and come in both reduced and official weights. They’re softer, and help young players overcome their fear of the ball. Unlike old safety balls, they generally perform like regular balls, bouncing and rolling true to expectations.