Skip to Content

The Anatomy of a Baseball

Following the discussion on the different types of baseballs that define the essence of baseball, I felt compelled to write a sequel that digs deeper into the iconic ball. From the meticulously stitched seams that dictate the flight of the ball, to the layers that comprise its core, each element plays a pivotal role in every pitch, swing, and catch.

After years of playing and collecting thousands of baseballs, I’ve decided to take few apart so that we can peek under the layers of a baseball to explore its core, the intricate winding that keeps it together, the tough skin that takes all the hits, and the stitches that add that perfect curve to your pitch.


Outer Shell (leather cover)

The first thing you’ll notice about any baseball is the feel. Quality baseballs have a subtle texture and grip that feels just right. On less expensive youth baseballs with synthetic covers, the touch feels waxy and slippery.

Back in the day, horsehide was the go-to material for baseball covers, reigning supreme until 1974, when the game switched over to cowhide due to a shortage of horsehide. Cowhide, despite being pricier and slicker, became the new standard, largely because of its availability. This allowed Rawlings to continue producing MLB game balls without a hitch.


In Japan, pitchers still prefer the grip and durability of horsehide balls. When we talk about leather, the variety increases with grades ranging from bonded to genuine, split-grain, and full-grain (or premium), each offering its own set of advantages.

Genuine leather, the traditional choice, offers longevity and a better grip, making it a favorite among youth leagues. The most expensive? Full-grain or premium leather, valued for its top-notch durability and breathability. Then there’s synthetic leather, a practical choice for practice balls, thanks to its resistance to dirt and water.

If you want to learn more about the types of baseball covers, I recommend that you read my other post, Which is Better – Leather Baseball or Synthetic Baseball.

Stitches on a Baseball

Every baseball is stitched together with 108 double stitches, usually in classic red, though other non-traditional colors are available. These stitches, which define the baseball’s seams, are categorized into three types: flat, rolled, or raised.

  • Raised seams are primarily for beginners, improving air grip for enhanced control
  • Rolled seams are mainly found in college and professional games at the Double-A level or below
  • Flat seams are used in Major League and Minor League (Triple-A) games, designed to decrease air resistance and increase pitch speed.

Want to read more about the history of baseball stitches? Read my post, Baseball Stitches – How Many Stitches Are there.



The term “winding” refers to the process and the layers of tightly coiled thread that are wrapped around the ball’s core. This core might be a cork, rubber, or a combination of both, known as a cork-and-rubber center. The winding is crucial for several reasons:

  1. Density and Hardness: The tightness of the winding determines the density and hardness of the baseball. More densely wound threads contribute to a firmer ball, which is desirable for professional play because it can be thrown faster and hit farther.
  2. Shape and Size: The winding process helps in maintaining the baseball’s shape and size. Consistent winding ensures that the ball is perfectly round and meets the official size regulations for league play.
  3. Durability: Tightly wound threads contribute to the baseball’s durability. A well-wound ball can withstand the impact of being hit by a bat multiple times without losing its shape or structural integrity.
  4. Performance: The way a baseball is wound affects its performance, especially in terms of how it reacts when pitched, hit, or caught. The layers of winding beneath the leather cover can influence the ball’s bounce, its aerodynamics, and how well pitchers can grip and control their throws.

This winding is typically done with wool, a blend of wool and synthetic fibers, yarn or any combination there of, which provides the right balance of elasticity, weight, and durability.

I wrote an in-depth post on the history and specifications of baseball stitches in my post, Threads Inside Baseballs so make sure to check it out.

Core of a Baseball

At the heart of a baseball is the core, or “pill,” which is made of premium cork, rubber, or a combination of both. However, any t-balls or training baseballs rated with SEV INDEX levels or RIF do not contain this cork center.


There are two main types of pills:

  • Cork and Rubber: This type of pill is a solid black ball comprising rubber mixed with bits of cork, then wrapped in wool
  • Cushioned Cork: Characterized by their red or orange outer colors, cushioned cork pills feature a small, ball-shaped piece of cork encased in two, half-round outer shells of black rubber, sealed with a red rubber gasket to ensure proper adhesive application. A layer of red (or orange) rubber is then molded over the black rubber encasement. Research has shown that baseballs with cushioned cork cores tend to outperform those with cork and rubber pills in terms of behavior and travel velocity.

The “pill” assembly forms a perfect circle, weighing approximately 7/8 ounces (24.80 grams) and measuring about 4 1/8 inches (10.48 centimeters) in circumference. After the pill is molded, it, along with others, is placed in a spinning drum where a thin layer of cement is applied to its surface. This adhesive helps to secure the wool yarn to the pill at the start of the winding process.

Please read me post, Types of Baseball Cores – From Rubber to Cork Pills for additional information.

In Closing

In this post, we’ve explored various components that transform baseballs into marvels of design and craftsmanship. From the core to the cover, the winding to the precision stitching, each component plays an important role in a baseball’s performance on the field. The choice between horsehide and cowhide, the seam types that affect the game’s rhythm, and the specific materials chosen for durability and performance highlight that a baseball is far more complex than it appears.

So, the next time you see a fastball whipping into the catcher’s mitt or a home run clearing the outfield fence, think of the intricate details and rich history encapsulated within each baseball.

I highly recommend visiting my reference page, “Buying Baseballs – Reference Articles,” to gain a comprehensive understanding of baseballs.

If you found this post to be helpful, please do me a favor and sign up for my newsletter.