Bearing dimension reference.
Common ball bearings — bore, outside diameter, and width for 6xxx-series single-row deep-groove bearings. The cross-reference between number designation and physical size.
The chart
| Bearing number | Bore (mm) | OD (mm) | Width (mm) | Series / Notes |
|---|---|---|---|---|
| 608 | 8 | 22 | 7 | Skateboard / fidget spinner standard |
| 6000 | 10 | 26 | 8 | Light (60xx) |
| 6001 | 12 | 28 | 8 | Light series |
| 6002 | 15 | 32 | 9 | Light series |
| 6003 | 17 | 35 | 10 | Light series |
| 6004 | 20 | 42 | 12 | Light series |
| 6005 | 25 | 47 | 12 | Light series |
| 6006 | 30 | 55 | 13 | Light series |
| 6007 | 35 | 62 | 14 | Light series |
| 6008 | 40 | 68 | 15 | Light series |
| 6200 | 10 | 30 | 9 | Medium (62xx) — most common general-purpose |
| 6201 | 12 | 32 | 10 | Medium series |
| 6202 | 15 | 35 | 11 | Medium series |
| 6203 | 17 | 40 | 12 | Medium — typical small electric motor |
| 6204 | 20 | 47 | 14 | Medium series |
| 6205 | 25 | 52 | 15 | Medium — common gearbox bearing |
| 6206 | 30 | 62 | 16 | Medium series |
| 6207 | 35 | 72 | 17 | Medium series |
| 6208 | 40 | 80 | 18 | Medium series |
| 6209 | 45 | 85 | 19 | Medium series |
| 6210 | 50 | 90 | 20 | Medium series |
| 6300 | 10 | 35 | 11 | Heavy (63xx) — higher load capacity |
| 6301 | 12 | 37 | 12 | Heavy series |
| 6302 | 15 | 42 | 13 | Heavy series |
| 6303 | 17 | 47 | 14 | Heavy series |
| 6304 | 20 | 52 | 15 | Heavy series |
| 6305 | 25 | 62 | 17 | Heavy series |
| 6306 | 30 | 72 | 19 | Heavy series |
| 6307 | 35 | 80 | 21 | Heavy series |
| 6308 | 40 | 90 | 23 | Heavy series |
How bearing numbers work. For 6xxx-series ball bearings: the first digit (6) indicates single-row deep-groove ball bearing. The second digit is the series — 0 (extra light), 2 (medium), 3 (heavy), reflecting load capacity. The last two digits indicate bore: for digits ≥ 04, multiply by 5 (so 6206 = 30 mm bore). For 00-03, bore is 10/12/15/17 mm respectively. Width and OD scale with the series.
Common applications
| Application | Typical bearing | Why |
|---|---|---|
| Skateboard / fidget spinner | 608 | 8 mm bore standard |
| Inline skate wheel | 608 | Same as skateboard |
| Small electric motor (washer, fridge) | 6203, 6204 | Common shaft sizes |
| Larger electric motor (5 HP) | 6205, 6206 | 25-30 mm shaft |
| Automotive wheel hub | Tapered roller | Not 6xxx — uses tapered roller bearings |
| Bicycle wheel hub (loose ball) | 1/4" balls | Older designs; modern uses sealed cartridges |
| Bicycle bottom bracket (cartridge) | 6804, 6805, etc. | Thin-section bearings (68xx series) |
| Industrial pillow block bearing | 6206, 6208 | Mounted in housing for shaft support |
| High-speed spindle (machine tool) | Angular contact | Not 6xxx — uses 7xxx series for axial load |
| Conveyor roller | 6204, 6205 | Plus seals for dust resistance |
Common pitfalls
- Bearing number tells you size, not service condition. A 6205 ZZ (with metal shields), 6205 2RS (rubber seals), 6205 C3 (looser radial clearance), and 6205 P5 (higher precision) all have the same dimensions but different sealing, clearance, and tolerance. The suffix matters.
- Radial vs angular contact bearings. 6xxx series carries mostly radial load. For combined radial + axial, use angular contact (7xxx) or tapered roller. A 6xxx bearing under significant axial load will fail.
- Bore tolerance and shaft fit matter. A 25 mm bore bearing has a specific tolerance (typically -0.000/-0.010 mm). The shaft must be sized for press fit (k5/k6/n6) or sliding fit (g6/h6) depending on whether the inner race rotates or is stationary.
- Speed limits depend on lubrication. A 6205 ball bearing can run at 12,000+ rpm with grease, 20,000+ rpm with oil. Above these limits, heat builds up faster than it can dissipate.
- 'Sealed for life' isn't. Sealed bearings (2RS, 2Z) are good for 5-10 years in normal service, but seal life depends on temperature, dust exposure, and rotation speed. Hot or dirty environments shorten service life significantly.
Common questions
What does the 6200 series number mean?
It's a size code. The first digit (6) means deep-groove ball bearing; the second (2) is the series (light duty). The last two digits multiplied by 5 give the bore diameter for sizes 04 and up. So a 6204 has a 20 mm bore (04 × 5 = 20). Sizes 00-03 are exceptions: 00 = 10 mm, 01 = 12 mm, 02 = 15 mm, 03 = 17 mm.
What's the difference between 6200 and 6300 series?
Same bore diameters, but 6300 is heavier duty — bigger outer diameter, thicker rings, higher load capacity. A 6204 and a 6304 both fit a 20 mm shaft, but the 6304 is physically larger overall and handles roughly 50% more radial load. Use 6300 when shaft sizes are fixed but loads are high.
How do I identify a sealed vs shielded bearing?
Sealed bearings (suffix 2RS, RS, or DDU) have rubber lips that contact the inner race — better at keeping contamination out but creates friction. Shielded bearings (suffix ZZ, 2Z, or Z) have metal shields with a small gap — lower friction but less protection. For a wet or dusty environment use sealed; for high-speed clean applications use shielded.
What does '608' mean and why is it everywhere?
608 = deep-groove ball bearing, light series, 8 mm bore. It's the standard skateboard wheel bearing, also used in fidget spinners, fans, and many small motors. Cheap, mass-produced, available in literally millions of variants. Outer diameter is 22 mm, width 7 mm.
Are 608ZZ and 608RS interchangeable?
Mechanically yes — same bore, OD, width, and load rating. The difference is the seal. 608ZZ (metal shielded) is fine for skateboards and fans where dust isn't constant. 608RS or 6082RS (rubber sealed) is better for wet, dirty environments at the cost of slightly higher rolling resistance.
Sources
- Bearing dimension standards: ISO 15 — Rolling bearings — Radial bearings — Boundary dimensions, general plan.
- ABMA standards (US): ABMA Standard 20 — Radial Bearings of Ball, Cylindrical Roller and Spherical Roller Types — Boundary Dimensions.
- Tolerance grades: ABMA Standard 20 and ISO 492.
- Designation system: ISO 15, with manufacturer-specific extensions (SKF, FAG, Timken catalogs).
Disclaimer. Bearing selection requires load analysis (radial, axial, dynamic, static), speed, lubrication, temperature, and environment. For critical applications, consult bearing manufacturer catalog or engineering reference.