How to Identify a Bearing Model Before You Order
The most common ways a bearing order goes wrong: suffix mix-ups, metric vs inch bores, and unit vs insert confusion. With a pre-order check.
Most wrong bearing orders are not caused by a wrong size. They are caused by a right size with the wrong letters: a missing seal suffix, a clearance nobody mentioned, an inch bore read as metric, or a complete unit ordered when only the insert was needed. Each of these produces a bearing that fits on the shelf and fails on the machine. This page lists the mix-ups we see, explains how to read a bearing designation, and ends with a pre-order check you can copy.
How to read a bearing designation
A designation has up to three parts. Take a 6205-2RS/C3:
| Part | Example | Meaning |
|---|---|---|
| Prefix | (none here) | Material, special design or part of a bearing, for example a component only |
| Basic number | 6205 | Type (6 = deep groove ball), series (2 = light) and bore (05 x 5 = 25 mm) |
| Suffix | -2RS/C3 | Seals on both sides; internal clearance group C3 |
For bores from 20 mm to 480 mm in most metric series, the last two digits times five give the bore in millimetres: 6205 has a 25 mm bore, 6310 a 50 mm bore. Bore codes 00, 01, 02 and 03 are exceptions: 10, 12, 15 and 17 mm.
The suffix is where most mistakes happen. Prefix and suffix letters are easy to leave out of an inquiry, and they decide what the factory makes. A quote for “6205” is a quote for an open bearing with normal clearance.
Common mix-ups and how to avoid them
1. Seal and shield suffixes. 6205, 6205-Z, 6205-ZZ and 6205-2RS have the same dimensions and different closures. Different makers write the same closure in different ways: ZZ, 2Z and -2Z are metal shields on both sides; 2RS, 2RS1 and DDU all mean contact seals on both sides. If you read the suffix from a branded bearing, give the original as well as your interpretation.
2. Clearance not stated. No clearance mark means C0. If the bearing came out of a motor or another warm-running position, look closely for C3 on the ring. A case from our own records: a domestic customer in China ordered 6205 bearings without stating a clearance, so the factory produced the standard C0. The customer passed the batch to a drum manufacturer, and that application had to control the drum’s wobble tightly, which called for C2. The batch came back. The factory re-checked the clearance of every bearing and re-supplied the order. One line in the inquiry would have avoided it.
3. Specifying a clearance that does not fit the application. The reverse also happens. In 2004 a customer in Singapore ordered cylindrical roller bearings specified as C4. After delivery it turned out that C4 did not suit the actual application: the clearance was too large. If you are changing clearance from the original, check the reason first. For motor bearings, the electric motor bearing page explains why C3 is common there. The bearing internal clearance guide explains when each group is used.
4. Similar numbers, different bearings. Some designations differ by one digit and describe a different bearing:
| You meant | Easily confused with | Difference |
|---|---|---|
| 6205 (deep groove ball) | 62205 | 62205 is a wider, double-sealed version with the same bore and outside diameter |
| 30205 (tapered, 16.25 mm wide) | 32205 (tapered, 19.25 mm wide) | Same bore and outside diameter, different width and load rating |
| 6205 | 6305 | Same bore, larger outside diameter and width |
| 22205 (spherical roller) | 2205 (self-aligning ball) | Different bearing type, same boundary size |
5. Metric vs inch bores. Inch bearings and inserts are common in North American equipment. An inch insert keeps the same housing size but has a dash number for the bore in sixteenths of an inch: UC207-20 is 1-1/4 in, UC207-22 is 1-3/8 in, UC208-24 is 1-1/2 in. A metric UC207 (35 mm) will not fit a 1-3/8 in shaft (34.9 mm) properly. Measure the shaft, not just the old bearing. The inch bore pillow block page lists the common inch sizes.
6. Unit vs insert vs housing. UCP208 is a complete pillow block unit: a P208 housing with a UC208 insert. UC208 is the insert alone. If you only need to replace a worn insert, ordering the complete unit means paying for a housing you do not need; ordering the insert when the housing is cracked leaves you short. State which one you want: complete unit, insert only or housing only.
7. JIS vs ISO housing dimensions. The same unit designation can have different bolt spacing under JIS and ISO 3228. A UCP204 has a 95 mm bolt spacing under JIS and 96 mm under ISO 3228. Mixing up neighbouring housing sizes is another trap: a buyer measuring 137 mm between the bolt holes is looking at a P208 housing, not a P207, whose standard spacing is 127 mm. Measure bolt spacing and centre height on the old unit and compare them with the UCP 200 series table.
8. OEM part numbers. Equipment and vehicle makers number bearings in their own systems. An OEM number is not wrong, but it has to be matched to the standard bearing it represents. Send the OEM number with dimensions and a photo; we confirm the standard model before quoting.
9. Tapered bearing parts. A tapered roller bearing is a cone (inner ring with rollers and cage) and a cup (outer ring). Metric designations such as 30205 cover both. Inch tapered bearings have a separate number for the cone and the cup. Say whether you need the complete bearing, the cone only or the cup only.
How to cross-reference a branded number
Brand designations mostly follow the international standard numbers, but suffixes differ from maker to maker. Our technical staff first look the number up in professional bearing reference handbooks, then check it against published online catalogs. You can start with our cross-reference pages: SKF, NSK, NTN, Koyo and Nachi, Timken and pillow block units. These pages compare dimensions for interchange; they do not compare quality.
Pre-order check
Copy this list and tick it before you send an order:
- Full designation copied from the old bearing, with every prefix and suffix.
- Bore, outside diameter and width measured and checked against the designation. The bearing size finder helps here.
- Closure stated: open, single shield, double shield or double seal.
- Clearance stated, or confirmed as normal.
- Metric or inch bore confirmed by measuring the shaft.
- For mounted units: complete unit, insert only or housing only; bolt spacing and centre height measured.
- For tapered bearings: complete bearing, cone or cup.
- OEM numbers sent with dimensions and a photo.
- Any special requirement stated: noise grade, grease, precision class.
- The supplier’s specification sheet read line by line before production.
The last point is your safety net. At FULI each model is confirmed on our own specification sheet before production, and anything we cannot supply exactly as asked is marked as an exception on the same sheet rather than substituted. Send your list to sales@fuli-bearings.com or through the contact page. The quotation request template puts this check into an inquiry you can copy, and the bearing buying guide covers the steps after the order.
Backed by 20+ years of bearing export experience in Linqing, Shandong. FULI ships to 50+ countries & regions.
FAQ
How do I identify a bearing model number?
Read the number on the side face of the ring, or on the shield or seal. Copy every letter and digit, including prefixes and suffixes such as 2RS, ZZ or C3. If nothing is readable, measure the bore, outside diameter and width with a caliper and look the size up in a dimension table.
Is a 6205 the same as a 6205-2RS?
They have the same dimensions, but a 6205 without a suffix is an open bearing, while a 6205-2RS has a rubber seal on both sides and leaves the factory greased. They are not interchangeable in every machine: an open bearing in a dirty position fails early, and a sealed bearing in an oil bath cannot take in the oil.
What does C3 mean on a bearing?
C3 is an internal clearance group larger than normal (C0). It is used where fits and temperature reduce clearance in service, such as electric motors. A bearing with no clearance mark is C0.
How do I know whether a pillow block is metric or inch?
Measure the shaft. Metric inserts have a plain number such as UC207 for a 35 mm shaft. Inch inserts add a dash and the bore in sixteenths of an inch, such as UC207-20 for a 1-1/4 in shaft or UC207-22 for 1-3/8 in.
Can I order a bearing using an OEM part number?
Yes, but the OEM number has to be matched to the standard bearing it stands for. Send the OEM number together with the dimensions and a photo, and the supplier confirms the standard model before quoting.