How to Identify Bearing Size and Types

How to Identify Bearing Size and Types

Whether you're repairing an RC vehicle, rebuilding a fishing reel, maintaining industrial equipment, or working on a custom project, correctly identifying a bearing is the first step toward finding the right replacement.

At FastEddy Bearings, one of the most common questions we receive is:

"How do I know what bearing I need?"

Fortunately, identifying most bearings is easier than many people think.

Start With the Bearing Number

The easiest way to identify a bearing is by reading the number etched on the shield or seal.

  • 685
  • 695
  • 6805
  • 6902
  • MR85
  • MF85
  • R188

If the bearing number is visible, simply search the number on FastEddyBearings.com to find the correct replacement.

Measure the Bearing

When the number is unreadable, measure the bearing using a digital caliper.

You need three measurements:

Inner Diameter (ID)

The hole through the center of the bearing.

Outer Diameter (OD)

The outside of the bearing.

Width

The thickness of the bearing.

Bearing sizes are written as ID × OD × Width.

Example:

  • 5mm ID
  • 10mm OD
  • 4mm Width

This bearing would be identified as 5x10x4.

Identifying Shield and Seal Types

Rubber Sealed Bearings

  • Rubber seals
  • Better dirt protection
  • Longer service life
  • Most common in RC vehicles

Common markings:

  • 2RS
  • RS

Metal Shielded Bearings

  • Thin metal shields
  • Lower rolling resistance
  • Less contamination protection
  • Common in electric motors and gearboxes

Common markings:

  • ZZ
  • Z

Open Bearings

  • No seals
  • No shields
  • Lowest friction
  • Require regular maintenance

Identifying Flanged Bearings

Flanged bearings have a lip on the outer race.

  • Steering systems
  • Bellcranks
  • Wheel hubs
  • Servo savers
  • Industrial equipment

Identifying One-Way Bearings

One-way bearings rotate freely in one direction and lock in the opposite direction.

  • Nitro engine starter systems
  • Pull-start systems
  • Helicopter drivetrains

Identifying Spherical Bearings

  • Ball-shaped center
  • Allows angular movement
  • Used in suspension systems
  • Common in racing applications

Identifying Ceramic Bearings

  • Reduced friction
  • Improved corrosion resistance
  • Longer life
  • Increased efficiency

Identifying Stainless Steel Bearings

  • Fishing reels
  • Marine applications
  • Wet environments

Common Bearing Markings

  • RS – Single rubber seal
  • 2RS – Rubber seals on both sides
  • Z – Single metal shield
  • ZZ – Metal shields on both sides
  • F – Flanged bearing
  • MR – Miniature metric bearing
  • R – Inch-sized bearing

Why Correct Identification Matters

  • Poor fitment
  • Excessive wear
  • Reduced performance
  • Premature failure

Frequently Asked Questions

Can I identify a bearing without the number?

Yes. Measure the ID, OD, and width using a digital caliper.

Are rubber sealed bearings better than shielded bearings?

For most RC applications, rubber sealed bearings provide better contamination protection.

Can I replace a flanged bearing with a standard bearing?

Not always. The housing design must be checked first.

Final Thoughts

Learning how to identify bearing types is an essential skill for RC enthusiasts, fishermen, manufacturers, machine shops, and hobbyists alike.

At FastEddy Bearings, we stock over 8,000 bearings for RC vehicles, fishing reels, manufacturing, prototyping, and industrial applications. If you're unsure what bearing you need, we're always happy to help.

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