How to Read a Bearing Number

The Basic Structure

A bearing number like 6205-2RS contains three layers of information: the series (what type), the size (what dimensions), and the suffix (what features).

The first digit identifies the bearing type. In the ISO system used by most manufacturers:

6 — Deep groove ball bearing

7 — Angular contact ball bearing

N or **NU** — Cylindrical roller bearing

22 — Spherical roller bearing

30 or **32** — Tapered roller bearing

12 or **11** — Self-aligning ball bearing

The second digit indicates the width series (how narrow or wide), and the last two digits encode the bore diameter. For bearings 04 and above, multiply the last two digits by 5 to get the bore in millimeters. So 6205 = deep groove ball bearing, 200 series, 25mm bore.

Common Bore Codes

The bore code (last two digits) follows a simple rule for most sizes:

For codes 04 and above, multiply by 5. Codes 00–03 are special cases that must be memorized.

Suffixes — Seals, Shields & Features

The suffix tells you about sealing, clearance, and special features:

Seals & Shields:

2Z or **ZZ** — Metal shields on both sides (for moderate contamination protection)

2RS or **2RS1** — Rubber contact seals on both sides (for dust and moisture)

2RZ — Non-contact rubber seals (lower friction than 2RS)

No suffix — Open bearing (requires external sealing)

Clearance:

C3 — Greater than normal internal clearance (for temperature expansion)

C2 — Less than normal clearance (for precision)

No suffix — Normal clearance (CN)

Cage:

M — Brass cage

TN or **P** — Polymer cage

For example, 6205-2RS1/C3 is a deep groove ball bearing, 25mm bore, with rubber seals and C3 clearance.

Manufacturer Differences

While the base number is standardized (ISO 15), suffix conventions differ:

The core designation (6205, 6308, etc.) is always the same across brands. Only the suffix notation varies. Our cross-reference tool handles these translations automatically.