When buying bearings, you’ve probably noticed long strings of letters and numbers on every product box or datasheet. While they might seem cryptic, these part numbers—or bearing codes—hold the key to understanding exactly what type of bearing you’re dealing with.

Learning how to decode these part numbers can help you:

• Select the right bearing for your application
• Save time during replacements
• Avoid costly mistakes due to mismatched parts

In this article, we’ll show you how to read bearing numbers and what each section means.

Need bearings urgently? Visit our online store at Rodavictoria USA, email us at info@rdvbearings.com, or call us at +1 (954) 530-1454. We’ll help you find exactly what you need!

Why Do Bearings Have Part Numbers?

Manufacturers like KOYO, SKF, NTN, and others follow standardized systems for bearing codes. These codes help:

• Identify bearing type (e.g. deep groove ball, roller, needle)
• Indicate dimensions (inner diameter, outer diameter, width)
• Specify clearance (like C3 or C4)
• Describe sealing type (rubber seals, shields, etc.)
• Note precision level or special features

Once you learn the logic behind these numbers, it becomes much easier to find the right bearing for any machinery or project.

The Basic Structure of Bearing Part Numbers

Let’s break down a typical bearing number:

Example: 6303 2RS C3

Here’s what each part means:

1. Bearing Series (First Digit or Two)

• The first 1–2 digits show the bearing type or series:
  • 6 → Deep Groove Ball Bearing
  • 7 → Single Row Angular Contact Ball Bearing
  • 2 → Spherical Roller Bearing
  • 3 → Tapered Roller Bearing

So in 6303, the “6” means it’s a deep groove ball bearing.

2. Dimension Series (Next Digit)

• The next digit indicates bearing robustness (the series):
  • Light, Medium, Heavy
  • For example:
    • 0 → Extra light
    • 2 → Light
    • 3 → Medium

In 6303, the “3” refers to a medium series bearing.

3. Bore Size (Last Two Digits)

• The last two numbers (usually multiplied by 5) give the inner diameter (ID) in millimeters.

Examples:

• “03” → 3 x 5 = 15 mm bore
• “04” → 4 x 5 = 20 mm bore
• “10” → 10 x 5 = 50 mm bore

Thus, in 6303, “03” means a 17 mm bore (this is one exception where 03 = 17 mm instead of 15 mm).

4. Suffixes and Prefixes

Suffixes tell you about:

• Seal type:
  • 2RS = Two rubber seals
  • ZZ = Two metal shields
• Clearance:
  • C3 = Greater internal clearance than standard
• Precision:
  • P5 = Higher precision
• Special features:
  • NR = Snap ring groove
  • M = Machined brass cage

In our example 6303 2RS C3:

• 2RS → Sealed on both sides with rubber seals
• C3 → Greater internal clearance for higher speeds or temperature changes

Quick Reference Table

Why It Matters

Understanding bearing numbers helps you:
Avoid incorrect replacements
Save time identifying parts
Communicate effectively with suppliers
Order the right product confidently

Need Help Identifying Your Bearing?

Still confused by your bearing code? Don’t worry—we’re here to help.

Visit our website: Rodavictoria USA
Email us: info@rdvbearings.com
Call us: +1 (954) 530-1454

At Rodavictoria USA, we carry a wide range of bearings, pillow blocks, and oil seals, and our team of experts is ready to help you identify and choose the perfect product for your needs.

Empower yourself to decode bearing numbers—and keep your machines running smoothly.

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