The original metric part-numbering system for tapered roller bearings was based on the ISO 15 dimensional plan for radial bearings.

ISO introduced a new numbering system for tapered roller bearings in the ISO 355 plan. This numbering system uses three alphanumeric fields to define a dimension series. The bearing part number is defined by adding the inner ring bore diameter after the dimension series..

ABMA (inch) part numbers designed with metric envelope dimensions are identified with a J-prefix. Many of these part numbers have been assigned an ISO dimension series.The latest ISO 355 plan includes an expanded range of metric bearings originally designed by The Timken Company. These bearings are identified with a J-prefix.

ABMA standard 20 defines 5 classes: ABEC 1, ABEC 3, ABEC 5, ABEC 7, and ABEC 9. Instrument series ball bearings are defined in standards 12.1 and 12.2 and carry the suffix “P”. Extra thin and thin section ball bearings defined in standards 12.1 and 12.2 carry the suffix “T”. The higher the number of the classification, the tighter the tolerances become resulting in higher precision of the assembled bearing. When the classification system was first set up, machine tool technology was such that manufacturers mass produced only ABEC 1, and sometimes ABEC 3. Bearings for the higher classifications were selected from the production runs of the lower classification. Today, the technology has advanced to the point where manufacturers can produce ABEC 7 and ABEC 9 bearings routinely.