Skip to Content

Types of Baseball Cores – From Rubber to Cork Pills

I have seen my fair share of baseballs, from the ones we used back in T-ball to those high-flying college league and MLB balls. But have you ever stopped to think about what makes each of these balls tick? Well, it all starts with the core (a.k.a. pill).

So, why am I zeroing in on the core today? Simple. The type of pill and how it is wrapped up in different types of yarns make a huge affect on the performance of baseballs. Understanding the intricate details can help parents, coaches, and even the players themselves make informed choices.

In this post, we’ll dive deep into the core—or pill—of baseballs designed for multiple age groups, guiding you through the intricacies of how their varied constructions impact performance and suitability, as we dissect the differences and peel back the layers to reveal what makes each ball perfect for its league and age group.


Please note that within each age group, the design and materials used in a pill can vary among manufacturers.

Understanding the Baseball Core (Pill)

The core—or ‘pill’—serves as the epicenter of its performance characteristics, dictating the ball’s response upon impact, its durability, and overall behavior during play. The core’s composition, often a calculated blend of synthetic materials, cork, rubber, or both, is engineered with precision to fulfill specific performance criteria. This deliberate choice of materials is critical, as it directly influences the ball’s coefficient of restitution (COR) and its compression rating—key indicators of the ball’s liveliness and resistance to deformation under pressure.


For young players, a ball with a softer core is not merely a safety measure; it is essential for fostering confidence and skill development. A hard, unyielding core can be discouraging and potentially hazardous for novices. As players mature and progress, however, smaller, more “bouncy” core with tight windings become necessary to challenge their developing skills, providing the necessary feedback for precision and power in play.

The Heart of the Ball

The core composition of a baseball significantly varies across different age groups, each designed to suit the specific needs and safety requirements of players at each developmental stage. Please note that most baseballs intended for all age groups (except certain training balls) follow the MLB baseball standard (9″ circumference and 5 ounces in weight).



Pre-T-ball cores are almost always made from light, open-cell foam materials engineered to reduce impact and facilitate play for beginners. Furthermore, pre T-balls tends to be hollow with lower compression ratings, reducing bounce and speed to make them easier for children to hit and catch. The Soft-Strike’s cushy feedback and low coefficient of restitution (COR) values resemble tennis ball construction, providing a suitable transition from toddler to kindergarten play.


Designed for kindergartners, T-ball cores are crafted from open-cell foam with a solid structure. These cores boast greater elasticity and a lower hysteresis profile, enabling efficient shape recovery after impact and minimal energy loss during this process. Compared to Franklin’s Soft-Strike core, the cell size, shape, and distribution within these T-ball cores are more uniform.

Rawlings TVB T-balls, weighing approximately 5 ounces, match the standard baseball weight.


As players advance into youth baseball leagues, the composition of baseball cores evolves to strike a balance between softness for safety and firmness for enhanced playability. For children aged 6 to 8, baseballs typically feature two primary types of cores: a composite of cork and rubber, and a core constructed entirely of synthetic materials. The composite cores vary in size and the ratio of cork to rubber, with those intended for the older children in this age group usually containing a higher proportion of rubber.

The synthetic cores, manufactured to precise standards, are utilized in safety baseballs, which are specifically designed for youth play. These cores, made entirely from man-made materials, stand in contrast to the mixed composition of cork and rubber.


Recreational baseballs designed for ages 8-12 begin to introduce “livelier” balls, starting with a small core made of cork and rubber with a higher rubber content. Leagues prioritizing safety will opt for baseballs with safety cores, often designated as Level 10.

At this stage, children can swing harder, which can destabilize the cork cores, leading to misshapen baseballs, loose stitches, and seams, etc., rendering them unlikely to last more than a season.

Most competitive and tournament teams will bypass these types of baseballs, choosing instead to play with “regular” baseballs that have cork and rubber cores.


Competitive baseballs feature a small core, or “pill,” primarily composed of black rubber mixed with cork bits, approximately the same size as that used in regular MLB baseballs.

Children in recreational leagues typically begin using these balls around the ages of 13 to 14, whereas those in competitive or tournament leagues will start using it as early as the 8U (Under 8) level.

Baseballs constructed with cork and rubber cores are specially designed for use with metal bats, ensuring they do not travel as quickly or as far as regular baseballs.


In terms of construction, the materials and performance characteristics of the cores (or “pills”) used in tournament baseballs are virtually identical to those used in Major League Baseball (MLB) balls. Manufacturers introduce slight variations in the quality of the ball’s leather, the height of the seams, and the layers of wool windings to adjust the overall Coefficient of Restitution (COR) profile, which determines the baseball’s liveliness.

These red “pills” are commonly referred to as “cushioned cork center” or “double cushioned cork”. Tournament baseballs, typically used by players aged 16 and older, are quite expensive compared to youth baseballs.

In Closing

Through our exploration of baseball cores, from pre-T-ball to the professional leagues, it’s clear that each core is carefully crafted to align with the changing abilities and requirements of players as they advance through various phases of their baseball careers.

You might consider purchasing a bulk of “regular” baseballs to save money in the long run. However, from personal experience, I urge you to accurately evaluate the current age and skill level of your child or team before making a purchase. Opting for baseballs that suit their present needs will prove more beneficial.

For a comprehensive collection of baseball-related articles, please visit our Buying Baseballs – Reference Articles page.

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