# Basic designations

A basic designation typically contains three to five digits. Some products, like cylindrical roller bearings, can have a combination of alphanumeric characters. The basic designation system is shown in table 1. The number and letter combinations have the following meaning:
• The first digit or letter or combination of letters identifies the bearing type and eventually a basic variant.
• The following two digits identify the ISO dimension series. The first digit indicates the width or height series (dimensions B, T or H). The second digit identifies the diameter series (dimension D).
• The last two digits of the basic designation identify the size code of the bearing bore. The size code multiplied by 5 gives the bore diameter (d) in mm.
The most important exceptions in the basic bearing designation system are:
1. In a few cases the digit for the bearing type or the first digit of the dimension series identification is omitted. These digits are shown in brackets in table 1.
2. Bearings with a bore diameter of 10, 12, 15 or 17 mm have the following size code identifications:
00 = 10 mm
01 = 12 mm
02 = 15 mm
03 = 17 mm
3. For bearings with a bore diameter &lt; 10 mm, or ≥ 500 mm, the bore diameter is generally given in millimetres (uncoded). The size identification is separated from the rest of the bearing designation by an oblique stroke, e.g. 618/8 (d = 8 mm) or 511/530 (d = 530 mm). This is also true of  standard bearings in accordance with ISO 15:2011 that have a bore diameter of 22, 28 or 32 mm, e.g. 62/22 (d = 22 mm).
4. For some bearings with a bore diameter &lt; 10 mm, such as deep groove, self-aligning and angular contact ball bearings, the bore diameter is also given in millimetres (uncoded) but is not separated from the series designation by an oblique stroke, e.g. 629 or 129 (d = 9 mm).
5. Bore diameters that deviate from the standard bore diameter of a bearing are uncoded and given in millimetres up to three decimal places. This bore diameter identification is part of the basic designation and is separated from the basic designation by an oblique stroke, e.g. 6202/15.875 (d = 15,875 mm = 5/8 in).

## Series designations

Each standard bearing belongs to a given bearing series, which is identified by the basic designation without the size identification. Series designations often include a suffix A, B, C, D or E or a combination of these letters. These letters are used to identify differences in internal design.
The most common series designations are shown in table 1. The digits in brackets are omitted in the series designation.