What Bowling Balls Are Made Of? Are they hollow?

So what are bowling balls made of?

The outside shell of bowling balls can be made of urethane, plastic, reactive resin. In the past, they were also sometimes made of rubber. The middle of the ball is a mixture of tiny, glass microbubbles, filler material, and a (usually metal) core.

The rest of this article goes in-depth about each of these materials and the pros and cons of each one.

Are bowling balls hollow?

It’s a pretty common misconception that bowling balls are hollow. Bowling balls are NOT hollow. Even the super-light, six-pound kid’s ball has a non-hollow center.

Bowling balls are universally the same size. This gives some people the impression that in order to make bowling balls lighter, they make them hollow. However, the way bowling ball manufacturers make balls of different weights is that they use different densities of filler material. Light bowling balls use a very low-density filler material.

Hard Wood/Rubber

Early, primitive bowling balls were typically made of a hardwood material called lignum vitae. Wooden balls were used for many years until finally, the first rubber bowling ball was released called the “evertrue”. A few years later, Brunswick began producing a rubber that they called Mineralite, and rubber bowling balls really began to increase in popularity. Rubber bowling balls dominated both the recreational and competitive bowling scenes for approximately 60 years. Rubber balls are virtually obsolete and there is no compelling reason to use them in this day and age.

Polyester (plastic)

The next iteration of bowling balls came from an advancement in materials science that allowed ball manufacturers to produce polyester (plastic) balls.

To this day, plastic bowling balls are still commonly used by both recreational and competitive bowlers. The balls you see on the rack at bowling alleys to this day are almost always plastic. They are cheap to produce, durable, and work great for recreational bowlers who aren’t too concerned¬†with the performance of the ball.

Plastic balls get a very small amount of reaction on the lanes. Competitive bowlers often have multiple bowling balls, and one of them is typically a plastic ball that is only used to throw at spares.

Using a plastic ball allows you to mostly take the oil pattern out of the equation, and just throw straight at your spares.


The next advancement in bowling ball technology was polyurethane. Frequently referred to simply as “urethane”, polyurethane balls are made of a different material than actual urethane. However, in real life, and for the purposes of this article, I will join the falsehood and refer to them as “urethane”.

Urethane balls were a game-changer for bowlers because it generates much more friction on the lane than plastic or rubber, allowing the ball to hit the pocket, with much more entry angle, increasing the probability of a strike.

Urethane is still commonly used to this day for a variety of reasons by competitive bowlers. They are often used as both strike balls and spare balls. Urethane can effectively be used as a strike-ball in dry/broken down oil conditions, and are often used as a spare-ball because they don’t hook nearly as much as other high-end balls.

The best thing to ever happen to bowling… Reactive Resin!

Urethane balls were the peak of bowling technology for about ten years until the next leap of innovation revolutionized the sport of bowling forever. Reactive resins came into play and gave bowlers an insane amount of hook potential and ability to get strikes.

However, as a side note, the term “reactive resin” probably doesn’t mean what you think it means. The “resin” part of the term actually comes from the fact that in the production process the resin starts as a liquid and solidifies into the hard, tacky coverstock. The “reactive” comes not from the fact that it reacts on the lane but that during the manufacturing process, when additives are mixed in, the resin reacts and creates the porous, high-friction surface we all have learned to love.

Reactive resin balls can give you an aggressive, violent, snappy hook. Check out the video below to get an idea of how much a reactive resin ball can hook.

What is a bowling ball filled with?

Bowling balls have another technologically advanced component to them. The middle of the bowling ball consists of a weight block, and filler material.

The filler material is a combination of glass microbubbles, and a filler material that is dense and heavy. This allows manufacturers to adjust the weight of the ball while maintaining the same size of ball.

The other component is the weight block. The weight block can be thought of as the “engine” driving the ball into the pocket. Here is a diagram showing a few different weight blocks/cores:

Each core has an equilibrium of how it naturally wants to roll. If you roll the ball off-axis in relation to the core, it will attempt to reach equilibrium by changing direction.

Ball manufacturers have dialed in the science behind this and have tons of different cores available for different ball reactions. Some cores allow for a smoother, less aggressive hook, and other cores give you a snappy, violent hook.

With all these options, how do I pick a ball for myself?

Here at Bowling Is Easy, we have a few pages that could help you out. If you are a beginner, check out the Best Bowling Balls for Beginners article. Any of those balls would be a great choice for your first bowling ball.

However, if you have a good idea of what you are doing and how to bowl, and you want a ball with a ton of hook, you can check out the Bowling Balls with the Most Hook Potential.

Those articles are a good place to start, but one of the first things you should do is talk to your local pro shop and tell them you want to get a bowling ball. Not only will they help you pick the right one, but they will also measure your hand and drill the ball perfectly for your hand.

You can purchase the ball at Amazon, and have your pro shop drill it for you, or you can buy a ball directly from the pro shop.

Most pro shops prefer you to buy the ball from them and often will have free or discounted drilling rates/fees if you do. However, the ball itself will usually be much cheaper on the internet, so even if there is a drilling fee, you could come out on top by purchasing the ball online and having the shop drill it for you.

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