Bearing Nomenclature
Paste a bearing number such as 6205-2RS C3, UCP208 or 30206 and see each part explained: type, series, bore code, seal, clearance, housing type and size.
A bearing number is built from a type prefix, a size code and a string of suffixes. Read it in that order to understand any FULI part number.
Reading a ball or roller bearing number (example: 6205-2RS C3)
| Part | Meaning |
|---|---|
| 6 | Type: single row deep groove ball bearing |
| 2 | Diameter series: 6200 series (6000 is lighter, 6300 is heavier, same bore) |
| 05 | Bore code: 25 mm (see the bore code table below) |
| 2RS | Seal: two rubber seals, one on each side |
| C3 | Radial clearance: wider than standard — see C0 vs C3 clearance checklist |
Tapered roller bearings use a different prefix, for example 30206: the 302 identifies the tapered roller series and 06 is the bore code, read the same way. See tapered roller bearing for the full designation.
Bore code table
| Bore code | Bore d (mm) |
|---|---|
| 00 | 10 |
| 01 | 12 |
| 02 | 15 |
| 03 | 17 |
| 04 | 20 |
| 05 | 25 |
| 06 | 30 |
| 07 | 35 |
| 08 | 40 |
| 09 | 45 |
| 10 | 50 |
From 04 upward, the rule is code x 5 = bore in mm. This applies to deep groove ball, tapered roller and insert bearing numbers alike.
Reading a mounted unit number (example: UCFL208)
| Part | Meaning |
|---|---|
| UC | Insert family: wide inner ring, two set screws |
| FL | Housing style: flange, oval base, two bolts |
| 208 | Bore code 08 = 40 mm, in the 200 series |
Other housing-style letters: P for pillow block, F for flange (square, four-bolt), T for take-up. See mounted bearing for how the housing styles compare, or insert bearing for the UC, SB and SA insert families.
Seal and clearance suffixes at a glance
| Suffix | Meaning |
|---|---|
| (none) | Open, no shield or seal |
| ZZ | Two metal shields |
| 2RS | Two rubber seals |
| C3 | Radial clearance wider than standard |
| P6 | Precision class tighter than standard (P0) |
See open, ZZ or 2RS seal selector and bearing suffix meaning for how these compare across naming systems.
Send the full number as printed on the bearing to sales@fuli-bearings.com if any part is unclear — we confirm the exact specification before quoting.
FAQ
How do I find the bore size from the number alone?
Take the last two digits before any suffix. From 04 upward, multiply by 5 to get the bore in mm — 05 is 25 mm, 08 is 40 mm. Codes 00, 01, 02 and 03 are exceptions: 10, 12, 15 and 17 mm.
What is the difference between the prefix letters UC, SB and SA?
They are insert bearing families with different locking methods: UC locks with two set screws on a wide inner ring, SB locks with set screws on a narrower inner ring, and SA locks with an eccentric collar. All three fit the same housing bore sizes at a given number.
What do the letters after a housing number mean, such as UCP, UCF, UCT?
They describe the housing style: P for pillow block, F for flange (FL for the oval two-bolt flange), T for take-up. The number after the letters is the bore code, read the same way as on the insert itself.