What is a bowling ball thumb slug

Are you wondering why you need a thumb slug in a bowling ball? Don’t worry! This article will clear all your doubts.

If you’re active in bowling activities, you probably know about thumb slugs. In fact, most bowlers prefer using this attachment while bowling, while others see no advantage in thumb slugs.

The debate seems obvious as thumb slugs have pros and cons, but how about players who don’t even know the actual purpose? That’s where this article comes in, as it will clear all your doubts about thumb slugs and how it affects your game.

Excited! Let’s begin.

What is a bowling ball thumb slug?

Thumb slugs are often referred to as inserts or solids that help you get a better grip on the bowling ball. These slugs feature urethane or vinyl construction, designed to fit perfectly in the hole where your thumb rests.

You can customize these slugs to prepare the desired size and complement your hand grip while using a bowling ball. In short, a thumb slug can enhance your bowling performance by offering a better grip.

Should I use a thumb slug?

Practically, the fit and comfort depend on how comfortable you feel with a thumb slug drilled inside your thumb hole.

For instance, some players find thumb slugs comfortable, helping them to control their bowling action to get better results. On the other hand, some players do not find the fit comfortable, as drilling finger holes can make the ball inconsistent, making undesirable releases.

In short, you should try both ways before figuring out which works best for you.

How do you put a thumb slug in a bowling ball?

Installing a thumb slug in a bowling ball is straightforward, and you will have your insert installed within no time. However, ensure that you employ a professional if you don’t know what you are doing.

Here are the steps to put a thumb slug in a bowling ball.

  1. Rub your thumb slug with sandpaper to make it smoother.
  2. After drilling the hole, apply some glue on the side of the hole according to your preference.
  3. Take the thumb slug and insert it into the bowling ball using a hammer. The position of the slug will differ for a left or right-handed player, so ensure that you keep this thing in mind.
  4. Once you insert the slug, ensure it reaches the hole’s bottom.
  5. After settling the slug in the hole, place the bowling ball on the drilling press.
  6. Once you have the drill press at the slug’s center, begin the drilling process. Ensure that you drill all the way through the thumb slug to get the best results.
  7. After drilling the thumb slug, cut the unwanted part of the thumb insert to match the ball’s surface.

Voila! You have your thumb slug inserted.

Can you remove a thumb slug from a bowling ball?

Thankfully, you can remove a thumb insert from a bowling ball using some tools and patience.

For instance, you can use a screwdriver and a small saw to cut the old insert into sections and use the screwdriver to remove the pieces. Once you have the first section, the other sections come out with minimal fuss.

Why do bowlers use thumb slugs?

As mentioned earlier, the debate between supporters and non-supporters of thumb slugs has always vowed their perspectives.

However, the specific answer to why bowlers install thumb slugs might depend on personal preferences.

For instance, a bowling ball consists of multiple layers, including the coverstock, weight block, and core. Each layer has contrasting density and texture, so whenever you drill a hole in a bowling ball, you might experience inconsistencies on the ball’s surface.

Adding a thumb slug to a bowling ball allows bowlers to control the inconsistencies, increasing comfort and precision while bowling. In short, bowlers use thumb slugs to balance the inner materials and achieve a seamless feel.

How tight should a bowling thumb hole be?

It depends on how you grip a bowling ball and which hand you use while bowling. However, always ensure that a thumb slug must fit the hole tightly to get the best results.

Thumb Slug – Pros And Cons

Since there are split opinions about thumb slugs, there are some advantages and disadvantages associated with thumb slugs.


  • Thumb slugs improve consistency in a bowling ball.
  • Thumb inserts can offer better grip while delivering shots.
  • Thumb slugs can keep your fingers comfortable while bowling.
  • You can get better results from your shots with an effortless pendulum swing.
  • Thumb inserts balance the different layers inside your bowling ball and offer consistent performance.


  • Using a thumb slug makes changes to a bowling ball’s dynamics, so you must learn to control the ball with its new feature. So, it might take some time to master using a thumb slug.
  • Drilling a hole in a bowling ball is delicate and often recommended under professional guidance. In short, ensure that you install a thumb slug with accurate fittings.
  • If the thumb hole is small, you may experience swelling after extended bowling sessions.

Difference between thumb slug and thumb insert

Although thumb slugs are often referred to as inserts, they are quite different from one another.

For instance, bowlers who have dry skin will love thumb inserts as they allow effortless handling with a smooth texture. On the other hand, thumb slugs are perfect for bowlers who sweat a lot.

Thumb Slug vs. Thumb Insert

Both attachments offer excellent comfort and ease of handling. So, using one of them depends on personal preference and skin type.

However, ensure that you seek professional help while installing these attachments to get the best results.


Thumb slugs enhance your bowling performance and are worth considering if you want to regulate inconsistencies with your bowling ball.

A thumb slug can make your release comfortable, allow you to control your pendulum swing, and get you better results, once you master using thumb slugs.

We hope this article has cleared all your doubts regarding thumb slugs and will help you make an informed decision while installing one.