Bearing numbers are alphanumeric combinations that indicate the bearing type, boundary dimensions, dimensional and running accuracies, internal clearance, and other related specifications. They consist of basic numbers and supplementary symbols. The boundary dimensions of commonly used bearings mostly conform to the organizational concept of ISO, Bearing numbers consist of a basic number and supplementary symbols. The basic number indicates the bearing series (type) and the width and diameter series as shown in Table 6.5. Basic numbers, supplementary symbols, and the meanings of common numbers and symbols are listed in Table 6.6. The contact angle symbols and other supplementary designations are shown in successive columns from left to right in Table 6.6.  For reference, some examples of bearing designations are shown here: