How to Read a Bearing Part Number: A Quick Reference
Decoding bore size, series and suffix codes on SKF, FAG, NTN and NSK bearings.
A bearing part number looks like a random string, but it follows a code. Once you know the pattern, you can tell the type, bore size and special features from the number alone.
The basic structure
A number is usually read in three parts: a prefix (optional), the basic designation, and suffixes. The basic designation holds the type, the series (width and diameter) and the bore size.
The bore code
For most metric bearings, the last two digits of the basic number give the bore. For codes 04 to 96, multiply by 5 to get the bore in millimetres: 6205 has code 05, so the bore is 25 mm; 6210 has code 10, so the bore is 50 mm. The codes 00, 01, 02 and 03 stand for 10, 12, 15 and 17 mm.
Small bearings have the bore written directly. A 608 bearing has an 8 mm bore. A number with a slash, such as 62/22, gives the bore after the slash (22 mm).
The type and series
The first digits show the bearing type and series. Examples:
- 6xxx: deep groove ball bearing (62xx and 63xx are the common series).
- 7xxx: angular contact ball bearing.
- 1xxx and 22xxx: self-aligning ball bearing and spherical roller bearing respectively.
- NU, NJ, NUP, N: cylindrical roller bearings.
- 3xxxx: tapered roller bearing in the ISO series.
Common suffixes
The suffix after the basic number describes seals, clearance, cage and tolerance. These are the ones you will see most:
- 2RS or 2RSR: rubber seals on both sides. ZZ or 2Z: metal shields on both sides.
- C3: clearance larger than normal. C4: larger again.
- K: tapered bore (1:12), used with adapter sleeves.
- M, J, TN: cage type (brass, steel, polyamide). The letter differs between brands.
- P6, P5: tighter tolerance class.
- E: reinforced internal design, common in spherical roller bearings.
Brands differ in the details
The basic number is standard across brands, so a 6205 from one maker matches a 6205 from another. Prefixes and suffixes can differ in letter and meaning from brand to brand, so always confirm a special suffix with the supplier.
You can type any bearing number into our website and we will show the decoded dimensions where we have the base size in our tables.
Key Takeaways
- Last two digits of the basic number times 5 gives the bore (04 to 96).
- The first digits show the type and the series.
- Suffixes such as 2RS, C3 and K describe seals, clearance and bore taper.
- Check brand-specific suffixes before substituting.
This article is general guidance. For a recommendation for your own application, contact our engineering team. Look up a ball bearing size →