Guide
How to read a bearing number: prefix, basic designation and suffix
Decode standard bearing numbers such as 6205-2RS-C3, NU210-E, 22216-E-K-C3, 51104 and 608-ZZ: bearing type, dimension series, bore code and suffixes.
Bearing numbers look cryptic, but standard metric designations follow a consistent logic. Once you know it, a number such as 6205-2RS-C3 tells you the bearing type, its size and how it is sealed and fitted — before you open a catalog.
The three parts
A full designation is built from:
| Part | Example | What it tells you |
|---|---|---|
| Prefix (optional) | e.g. a component or material code | Part of a bearing, special materials or manufacturer-specific variants |
| Basic designation | 6205 | Bearing type, dimension series and bore — the standard size |
| Suffix(es) | -2RS-C3 | Closures, clearance, cage, internal design, precision, lubrication |
The basic designation is standardised and means the same thing across manufacturers. Prefixes and suffixes are much less uniform: each manufacturer has its own system. That is why “6205-2RSR” and “6205DDU” describe the same kind of bearing in different dialects. Our glossary entry on full designations explains why the suffix still matters for identity.
The basic designation
For most radial bearings the basic designation reads type – dimension series – bore code:
| Position | Meaning | Examples |
|---|---|---|
| Type | First digit(s) or letters | 1 = self-aligning ball, 2 = spherical roller, 5 = thrust ball, 6 = deep groove ball, 7 = angular contact ball, NU/NJ/N = cylindrical roller |
| Dimension series | Width and diameter series | 2 = light, 3 = medium, 22 = wide light, 23 = wide medium |
| Bore code | Last two digits | 05 = 25 mm |
Some type digits are left out by convention. A wide self-aligning ball bearing is written 2205, not 12205.
Bore codes
| Bore code | Bore diameter |
|---|---|
| 00 | 10 mm |
| 01 | 12 mm |
| 02 | 15 mm |
| 03 | 17 mm |
| 04 to 96 | code × 5 mm (04 = 20 mm, 05 = 25 mm, 10 = 50 mm, 16 = 80 mm) |
| /22, /28, /32 | Bore given directly in mm after a slash, for sizes between the 5 mm steps (e.g. 62/22 has a 22 mm bore) |
| /500 and above | Bore given directly for very large bearings |
| Single digit | Small bearings: the last digit is the bore in mm (608 = 8 mm bore) |
Worked examples
6205-2RS-C3
| Token | Meaning |
|---|---|
| 6 | Deep groove ball bearing |
| 2 | Diameter series 2 (light) |
| 05 | 25 mm bore |
| 2RS | Contact seals on both sides |
| C3 | Internal clearance greater than normal |
Size: 25 × 52 × 15 mm — see 6205. Read more about seals and shields and C3 clearance.
NU210-E
| Token | Meaning |
|---|---|
| NU | Cylindrical roller bearing; two flanges on the outer ring, none on the inner ring |
| 2 | Dimension series 02 (light) |
| 10 | 50 mm bore |
| E | Reinforced internal design (more or larger rollers) — the letter varies by manufacturer |
Size: 50 × 90 × 20 mm — see NU210. NJ210 and NUP210 share the dimensions but locate the shaft differently.
22216-E-K-C3
| Token | Meaning |
|---|---|
| 2 | Spherical roller bearing |
| 22 | Dimension series 22 |
| 16 | 80 mm bore |
| E | Internal design generation (manufacturer-specific) |
| K | Tapered bore (1:12) for adapter or withdrawal sleeve mounting |
| C3 | Clearance greater than normal |
Size: 80 × 140 × 33 mm — see 22216.
51104
| Token | Meaning |
|---|---|
| 5 | Thrust ball bearing, single direction |
| 11 | Dimension series 11 (thrust) |
| 04 | 20 mm bore |
Size: 20 × 35 × 10 mm (bore × outside diameter × height) — see 51104.
608-ZZ
| Token | Meaning |
|---|---|
| 6 | Deep groove ball bearing |
| 0 | Diameter series 0 |
| 8 | 8 mm bore (single-digit bore code for small bearings) |
| ZZ | Metal shields on both sides |
Size: 8 × 22 × 7 mm. The 608 is one of the most common small bearings in the world — skateboards, scooters, fans and 3D printers.
Common reading mistakes
- Treating the whole string as the size. 6205-2RS and 6205-ZZ are the same size; the suffix describes the variant.
- Reading 62/22 as 6222. The slash means the bore is given directly: 22 mm, not code 22 (110 mm).
- Assuming suffixes are universal. “E”, “C” or “K” can mean slightly different things for different bearing types and makers. Use the suffix dictionary as a guide and confirm with the manufacturer.
- Ignoring missing characters. A worn marking “620_” could be 6200 to 6209 — measure to confirm (see how to measure a bearing).
Apply it
Paste a full number into the bearing number decoder to split it into parts, or search the base size on the bearing reference. The size chart shows whole series at a glance. Untangling thousands of designations in a catalog is a part identification job — talk to us.
Methodology article using synthetic examples only; it states no manufacturer specifications. Independent technical review: not yet assigned. Found an error? Tell us.
