Reading bearing part numbers: what every digit and letter means

How a standard part number is built up

An ISO standard bearing part number has three main parts: the prefix, the basic number and the suffix. The basic number tells you the type and the size, while the suffix gives further detail such as the closure type, the cage and the clearance.

Example 1: 6205ZZ C3

Part of the code	What it means
6	Deep Groove Ball Bearing
2	Width / diameter series (62 series)
05	Bore code 05 = 5 × 5 = 25 mm
ZZ	Steel shields both sides
C3	Internal clearance greater than standard

The rule for reading the bore size

For bore codes of 04 and above, multiply the last two digits by 5 to get the bore in millimetres: 04 = 20 mm, 08 = 40 mm, 20 = 100 mm. The codes 00 = 10 mm, 01 = 12 mm, 02 = 15 mm and 03 = 17 mm are special cases you simply have to remember.

Example 2: 22310K

Part of the code	What it means
223	Double row spherical roller bearing, 223 series
10	Bore 10 × 5 = 50 mm
K	1:12 taper bore (for use with an adapter sleeve)

Common suffixes

Code	What it means
ZZ / 2Z	Steel shields both sides
2RS / DDU / VV	Rubber seals both sides
C2 / CN / C3 / C4	Internal clearance (tight → loose)
M / MB	Machined brass cage
TN / TYN	Polyamide cage
P5 / P4 / P2	Progressively higher precision classes
K	1:12 taper bore
E	Reinforced design for higher load capacity

Why it pays to read the code

Ordering by the main digits alone, without the suffix, can get you something that fits but is not right for the job — standard clearance when the application needs C3, or a polyamide cage where the temperature is too high for it. Always quote every letter of the code.