What Are Baseballs Made Of? Every Layer Inside an MLB Ball

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A baseball is built from the inside out: a cork and rubber center called the pill, wrapped in layers of wool and cotton yarn, covered in two figure eight pieces of cowhide and stitched together by hand with red thread. Rawlings has made every official Major League ball since 1977, at its factory in Costa Rica.

Equipment explained
Inside an official baseball
From the center out
1. Center
Cushioned cork pillA small cork sphere
2. Rubber layers
Two layers of rubber around the corkTogether called the cushioned cork center
3. First winding
About 121 yards of four ply gray wool yarn
4. Second winding
About 45 yards of three ply white wool yarn
5. Third winding
About 53 yards of three ply gray wool yarn
6. Finishing layer
About 150 yards of fine polyester and cotton yarnSmooths the ball before the cover goes on
7. Adhesive
Rubber cementHolds the cover in place
8. Cover
Two figure eight pieces of cowhideHorsehide was used until 1974
9. Stitching
108 double stitches of red waxed threadSewn by hand
Construction as described by Rawlings and MLB.

Why Wool

Wool yarn holds its shape and gives the ball its bounce, and it helps the ball return to round after being hit. The tension of the windings affects how lively a ball is, which is one reason MLB tests balls and stores them in humidors. Small changes in the seams or core have been blamed for home run spikes and drops in recent seasons.

Quick Facts

Fact Detail
Official supplier Rawlings, since 1977
Factory Turrialba, Costa Rica
Total yarn Roughly a third of a mile per ball
Before each game Every ball is rubbed with mud to remove its gloss

For how the seams are sewn, see how many stitches are on a baseball, and for why balls get muddy, see why MLB rubs mud on baseballs.

Related

How much does a baseball weigh · How many stitches on a baseball · How many baseballs are used in a game · Why MLB rubs mud on baseballs

Construction details from Rawlings.