Most industrial ball and roller bearings follow the same ISO numbering logic, so once you can read one brand's part number you can read almost all of them. Here's how to decode a typical designation like 6205-2RS C3.
The base number: type, series and bore
The first digit (or two) identifies the bearing type and dimension series — for example 6 = single-row deep-groove ball bearing, 22 = spherical roller bearing, NU = cylindrical roller bearing. The last two digits of the base number encode the bore (inner diameter).
- Bore codes 00 = 10 mm, 01 = 12 mm, 02 = 15 mm, 03 = 17 mm.
- From 04 upward, multiply by 5: 04 = 20 mm, 05 = 25 mm, 06 = 30 mm, and so on.
- So 6205 is a deep-groove ball bearing with a 25 mm bore; 6305 is the same bore in a heavier series.
Suffixes: seals, shields, clearance and cage
The letters and numbers after the base designation describe the build. These vary slightly by manufacturer, which is why the same physical bearing can look like it has different part numbers:
- Seals/shields: 2RS / 2RS1 / LLU = two contact rubber seals; ZZ / 2Z = two metal shields; OPEN = none.
- Internal clearance: C2 (less than normal), CN (normal), C3 / C4 (greater than normal — common in electric motors).
- Cage/material: brass (M / MA), polyamide (TVH / TN9), steel (J).
Why the 'same' bearing has different numbers across brands
SKF writes 6205-2RS1, FAG writes 6205-2RSR, NTN writes 6205LLU, NSK writes 6205DDU — all are a 25 mm-bore sealed deep-groove ball bearing. The base number is shared; the seal/clearance suffix is brand-specific. That's the key to cross-referencing.
Need a bearing sourced or cross-referenced?
If you have a worn bearing with a partially legible number, or a part from a brand you can't get, send us the designation (or a photo of the bearing) and we'll identify it and quote an equivalent. We source across all major bearing brands on request.