What Do All the Bowling Ball Numbers and Specs Mean?

Q: What is differential in bowling?

Differential shows how much a bowling ball can flare or hook. A higher differential means more hook potential and a stronger backend motion, while lower differential provides a smoother, more controlled roll.

Q: What’s the difference between symmetrical and asymmetrical cores?

Symmetrical cores are uniform and predictable, creating smoother motion. Asymmetrical cores have uneven shapes that generate quicker revs and sharper backend turns.

Q: What does intermediate differential mean?

Intermediate differential applies only to asymmetrical cores and measures the strength of the mass bias. Higher values create a sharper backend, while lower ones smooth out the motion.

Q: Which bowling ball specs are best for beginners?

Beginners should look for medium RG (2.52–2.56) and medium differential (0.026–0.046) balls, which provide a balanced, controllable motion for learning different lane conditions.

A Complete Guide to RG, Differential, Core Types, and Coverstock

If you’ve ever picked up a new bowling ball or browsed an equipment catalog, you’ve probably seen specs like RG, Differential, and Coverstock Type. Those numbers aren’t random, they tell you exactly how your bowling ball will react on the lane.

Understanding what these specs mean helps you choose the right ball for your style, speed, and lane conditions. Let’s break down each one in plain language.

🎳 Bowling Ball Core: The Engine Inside

Think of the core as the engine of the bowling ball. It’s the internal shape that controls how the ball stores and releases energy.

There are two main types:

Symmetrical Cores: Balanced and predictable. These create smooth, controllable motion which is great for consistency and medium conditions.
Asymmetrical Cores: Unevenly weighted, which makes them rev up faster and change direction more sharply. These are ideal for heavier oil or when you need a stronger backend reaction.

Your ball’s layout how the holes are drilled in relation to your Positive Axis Point (PAP) also affects how that core shape performs.

⚙️ RG (Radius of Gyration): How Quickly the Ball Starts to Roll

RG stands for Radius of Gyration, a measurement (in inches) that describes how mass is distributed inside the ball.

Low RG (2.46–2.51): The ball’s mass is closer to the center, so it revs up quickly and hooks earlier.
Medium RG (2.52–2.56): A balanced option for versatile reaction on most lane patterns.
High RG (2.57–2.80): The weight is pushed outward, which helps the ball conserve energy and go longer before hooking.

💡 Easy analogy: A low RG ball is like a figure skater pulling their arms in to spin faster; a high RG ball is like extending their arms to slow the spin.

Differential: How Much the Ball Can Flare

Differential measures the difference between a ball’s highest and lowest RG values. It tells you how much the ball’s axis migrates aka, flare potential, as it travels down the lane.

Low Differential (0.000–0.025): Less flare, smoother motion, and more control.
Medium Differential (0.026–0.046): Moderate flare and a balanced hook shape.
High Differential (0.047–0.060): Stronger track flare and more hook potential.

Higher differential means more surface of the ball touches the lane, which increases friction and hook. Lower differential balls stay smoother and more predictable.

⚖️ Intermediate Differential: For Asymmetrical Balls Only

Some high-performance balls list an Intermediate Differential which is a measurement that shows how strong the ball’s mass bias is.

A higher intermediate diff = a more defined, angular backend motion.
A lower intermediate diff = a smoother, more controllable shape.

This spec only applies to asymmetrical cores.

🧩 Coverstock: The Ball’s “Tires”

If the core is the engine, the coverstock is the tires. It makes the biggest difference because 75% of a ball’s motion comes from the cover’s surface.

There are three main types:

Reactive Solid: Strong mid-lane read, more traction in oil.
Reactive Pearl: Skids farther with a sharp backend.
Hybrid: Blends both for a balanced reaction.

You can fine-tune performance by adjusting surface grit:

Lower grit (1000–2000): Hooks earlier.
Higher grit (3000–5000 or polished): Skids longer and hooks later.

Quick Reference Chart:

🧠 Putting It All Together

Low RG + High Differential: Early, strong hook, ideal for heavy oil or high-speed bowlers.
High RG + Low Differential: Longer, smoother motion, great for dry or medium-dry lanes.
Surface Adjustments: Always test sanding or polish before competition; it changes how your ball reads the lane more than anything else.

It is important to note that all bowling balls have a time and place for when they will perform best. This information above is a general guide but ultimately a ball can be used on any condition depending on the factors. It is our job as a bowler to consider all the factors and make the best guesses and decisions when bowling.

When you know what the numbers mean, buying your next bowling ball becomes less about guessing and more about matching equipment to your game.

Final Thoughts

Learning what RG, Differential, and coverstock mean is one of the best ways to level up your bowling IQ. Whether you’re building your first arsenal or fine-tuning your tournament bag, understanding these numbers will help you make smarter choices and improve your consistency on the lanes.

Frequently Asked Questions About Bowling Ball Specs

What does RG mean on a bowling ball?
RG stands for Radius of Gyration. It measures how the weight is distributed inside the ball. A lower RG (around 2.46–2.51) means the ball revs up faster and hooks earlier. A higher RG (2.57–2.80) means it skids farther and hooks later down the lane.

What is differential in bowling?
Differential tells you how much a ball can flare or hook. A higher differential (0.047–0.060) means more hook potential and a stronger backend motion. Lower differential (0.000–0.025) gives a smoother, more controllable shape that’s ideal for dry lanes.

What’s the difference between symmetrical and asymmetrical cores?
Symmetrical cores are uniform in shape and create a smoother, more predictable roll. Asymmetrical cores have an uneven shape, which helps the ball rev up faster and make a sharper turn at the breakpoint.

What does intermediate differential mean?
Intermediate differential applies only to asymmetrical bowling balls. It measures how strong the mass bias is. A higher intermediate differential produces a sharper backend reaction, while a lower one gives a smoother transition.

Which bowling ball specs are best for beginners?
Beginners usually do best with medium RG (around 2.52–2.56) and medium differential (0.026–0.046). These specs provide a balanced reaction that’s forgiving and easier to control across different oil patterns.

Does surface grit affect ball motion more than RG or differential?
Yes. Surface finish has the biggest impact on ball motion, about 75% of it. Lower grit (1000–2000) makes the ball hook earlier, while higher grit (3000–5000 or polished) helps it skid longer before hooking.