LEARN · 2026-10-06
How to read bearing numbers: 6204, 608 and deep-groove ball bearing sizes
The deep-groove ball bearing numbering system — type, size series and bore code — with a size table for 608, 6000, 6200 and 6300 series and shaft / housing fit advice.
Anatomy of a bearing number
Take 6204: the first digit 6 means deep-groove ball bearing; the 2 is the dimension series (larger digits = larger outer diameter and width); 04 is the bore code.
| Bore code | Bore d |
|---|---|
| 00 | 10 mm |
| 01 | 12 mm |
| 02 | 15 mm |
| 03 | 17 mm |
| 04 and up | code × 5 mm (04 → 20 mm) |
Three-digit miniatures like 608 or 625 use the last digit as the bore directly (608 → 8 mm).
TIPZZ = two metal shields, 2RS / DDU = two rubber seals, C3 = larger-than-normal radial clearance.
Common sizes
| Bearing | Bore d (mm) | OD D (mm) | Width B (mm) |
|---|---|---|---|
| 608 | 8 | 22 | 7 |
| 623 | 3 | 10 | 4 |
| 625 | 5 | 16 | 5 |
| 626 | 6 | 19 | 6 |
| 688 | 8 | 16 | 5 |
| 6000 | 10 | 26 | 8 |
| 6001 | 12 | 28 | 8 |
| 6002 | 15 | 32 | 9 |
| 6200 | 10 | 30 | 9 |
| 6201 | 12 | 32 | 10 |
| 6202 | 15 | 35 | 11 |
| 6203 | 17 | 40 | 12 |
| 6204 | 20 | 47 | 14 |
| 6205 | 25 | 52 | 15 |
| 6300 | 10 | 35 | 11 |
Shaft and housing fits
- Rotating inner ring, normal load: shaft k5 / k6 (light interference).
- Stationary outer ring: housing H7 (clearance) or J7.
- Frequent disassembly: shaft h6 / g6.
Use the ISO fit tolerance calculator for exact deviations. For 3D-printed housings open the bore by 0.1–0.2 mm and print a test ring first.
FAQ
What size is a 608 bearing?
8 mm bore, 22 mm OD, 7 mm wide — the skateboard / fidget spinner / 3D-printer classic.
6204 vs 6304?
Both have a 20 mm bore, but the heavier 6304 is 52 mm OD and 15 mm wide for higher loads.
ZZ or 2RS?
ZZ shields have less friction for high speed; 2RS seals keep dust and water out better but run warmer.