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Are Bowling Balls Hollow?


Are bowling balls hollow? For most part of my life I believed they were hollow from the inside. However, it turns out I was wrong. Bowling balls are not hollow!

Since all bowling balls are the same size, it is normal to believe that the lighter bowling balls may be hollow from the inside. So, what is inside of a bowling ball? What are they made of? Let’s find out!

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What are Bowling Balls Made of?

Bowling balls have undergone various transitions, from wooden bowling balls made with Lignum vitae, rubber balls consisting of ever true to mineralite, and then reactive bowling balls made from urethane.

They have upgraded over time to bring stability and accuracy and tackle other hindrances the game had to face.

Today, these balls are made from polyester, urethane, resin, or a mixture of these materials. Their rates vary from polyester being the cheapest to resin bowling balls (reactive urethane) being the most expensive.

But What is a Reactive Bowling Ball?

A reactive bowling ball is a type of ten-pin made of a reactive resin material that provides increased hook potential and back-end reaction. The reactive cover stock is designed to grip the lane better, generating more friction and creating a stronger hook on the back end of the lane.

Do a Lot of People Use it?

This type of ball is ideal for players with higher ball speeds as it provides greater ball control and reaction on the lane. Intermediate and advanced players commonly use Reactive bowling balls, while entry-level players often use plastic or polyester balls.

Then there are tiny bowling balls. Tiny bowling balls are a miniature version of the actual game typically used as toys for children or to decorate game rooms. They often come with miniature ten-pins and a small version of a bowling lane.

It is usually sold as a whole set consisting of balls, pins, and lanes made in lightweight plastic. It is popular among fans as a collectible item in different colors and sizes.

Are Bowling Balls Hollow? What is Inside a Bowling Ball?

To put it simply, no. It is a huge misconception that bowling balls are hollow! A bowling ball typically has a foam or polymer filling inside its center, which helps to distribute its weight evenly.

The filling material can also affect the ball’s performance, including its speed and hook potential.

There are three main components inside a bowling ball:

The Core

This is the weight block at the center of the ball, which determines its weight distribution and influences its ball reaction on the lane.

It is the part of the ball covered by the cover stock and forms the ball’s inner shape. The core is typically made of solid material, such as polyester, urethane, or reactive resin, and can come in various shapes and designs.

The type of core used in a bowling ball can significantly affect its performance on the lane, and bowlers can choose a ball with a specific core design to fit their individual needs and play style. The core is an essential component of a bowling ball and significantly impacts its overall performance.


Cover Stock

This is the outer layer of material that covers the core, providing grip and determining the ball’s reaction on the lane.

Cover stocks can range from very low grit, resulting in a skid/hook reaction, to high grit, resulting in a hook/roll reaction.

Bowlers can choose a ball with a specific cover stock and finish to fit their needs and play style. The type of cover stock used in a ball and its finish can significantly affect the ball’s reaction on the lane, determining its hook potential, back-end reaction, and overall performance.

Inner Shell

This material layer surrounds the core, providing a smooth surface and helping distribute weight evenly.

The inner shell can be made of various materials, such as foam, gel, or plastic, and can be used in conjunction with different core designs to create a specific ball reaction on the lane.

The thickness and composition of the inner shell can be adjusted to fine-tune the ball’s weight distribution and overall performance.

Types of Bowling Ball Cores

The core of a bowling ball consists of a mixture of resin with either bismuth or graphite to create a ceramic texture. Some companies may also use iron oxide to induce a better center of gravity.

The ceramic or plastic-like structure of the core has a similar density. This is a crucial factor when it comes to bowling ball manufacturing. The density of a bowling ball should range from 14 to 15 pounds per gallon. It directly affects the ball’s weight and, thus, the ball’s momentum when rolling down the lane.

There are five main types of bowling ball cores:

Symmetrical Cores

They have a uniform weight distribution, leading to a straighter, less hooking ball path. It has a uniform weight distribution, resulting in a straighter, less hooking ball path.

Bowlers often use this core type with lower ball speeds or rev rates or who prefer a straighter ball reaction on the lane. Symmetrical cores can come in various shapes, including round, oval, and more complex shapes, but the weight distribution remains the same regardless of the shape.

The uniform weight distribution of a symmetrical core makes it easier for bowlers to control the ball, as it will not exhibit the same amount of hook as an asymmetrical core.

Asymmetrical Cores

Asymmetrical cores have a non-uniform weight distribution, leading to a more hooking ball path. Bowlers often use this core type with higher ball speeds or rev rates or who prefer a more aggressive ball reaction on the lane.

The non-uniform weight distribution of an asymmetrical core can create more hook potential, allowing the ball to turn more toward the pocket on the back end of the lane. Bowlers who use an asymmetrical core must have reasonable ball control and accuracy, as the added hook potential can also make the ball harder to control.

Pancake Cores

This core consists of two flat discs stacked on top of each other, resulting in a low RG (radius of gyration). RG is a measure of the mass distribution in a ball, and a high differential, which measures the difference between the maximum and minimum RG.

This combination of low RG and high differential creates a ball with a strong hook potential and back-end reaction. Advanced bowlers with high ball speeds and rev rates often use Pancake cores, as they provide greater ball control and reaction on the lane.

Drill-Through Cores

In this core, they have a hole drilled through the ball’s center, leading to a lower RG and higher differential. The size, shape, and position of the drill-through hole can be customized to fit the specific needs of the bowler, providing greater ball control and a more aggressive ball reaction.

Drill-through cores are often used by advanced bowlers who have high ball speeds and high rev rates, as they provide a greater level of ball control and reaction on the lane. This core type is often combined with an asymmetrical cover stock for even more tremendous hook potential and back-end reaction.

Multiple Density Cores

A multiple-density bowling ball core consists of different materials with different densities, creating a specific weight distribution (it is more precise). A multiple-density core can provide a more aggressive ball reaction, more significant hook potential, and improved back-end reaction compared to a single-density core.

Advanced bowlers with high ball speeds and rev rates often use this core type, as they provide greater ball control and reaction on the lane. The design and materials used in a multiple-density core can vary significantly between manufacturers and ball models, allowing bowlers to choose the right ball for their specific needs.

The cores play a vital role in the ball’s weight distribution, lane reaction, and hook potential.

What are Bowling Pins Made of?

Now that we know about bowling balls inside out, what are the pins made up of? Since the pins are supposed to be highly durable as they take on hits from these rolling spheres, they are carved out of laminated maple wood or synthetic material.

The laminated maple wood is denser and more robust than solid wood, providing excellent durability for the pin and resisting warping. Synthetic pins are made of plastic, lighter than wood pins, and more durable and resistant to breakage. This saves costs as they don’t have to be replaced repeatedly.

The bowling pins must conform to specific dimensions and standards for official competitions, regardless of the material.


Bowling balls are not hollow; they have a unique structure inside that directly affects the gameplay of the sport. Not only is bowling complex but also a very dynamic sport. Bowling has evolved over 5,000 years!

From an extraordinary manufacturing process to unique gameplay, bowling appeals to a broader audience daily, and millions of people continue to enjoy it worldwide. The modern version of the game, along with its new rules and technology, is the best version of the sport to date.

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