When the nominal inner diameter of the bearing is a non integer between 0.6 and 10mm, the inner diameter code is represented by the nominal inner diameter in millimeters, separated from the dimension series code by a “/”. For example, the deep groove ball bearing 618/2.5 represents an inner diameter of 2.5mm; When the nominal inner diameter is an integer between 1 and 9, the inner diameter code is represented by the nominal inner diameter in millimeters. For example, for deep groove ball bearings 625, the inner diameter is 5mm. However, for deep groove and angular contact ball bearing diameter series 7, 8, and 9, the inner diameter and dimension series codes are separated by “/”. For example, for deep groove ball bearings 618/5, the inner diameter is 5mm; When the nominal inner diameter is 10, 12, 15, and 17, the inner diameter codes are 00, 01, 02, and 03 in sequence, such as deep groove ball bearing 6201, which represents an inner diameter of 12mm; When the nominal inner diameter is between 20 and 480 (excluding 22, 28, and 32), the inner diameter code is the quotient of the nominal inner diameter divided by 5. The quotient is a single digit and needs to be added with “0” to the left of the quotient. For example, in the case of a deep groove ball bearing 6208, the inner diameter is 40mm; When the nominal inner diameter is ≥ 500 or equal to 22, 28, 32, the inner diameter code is  expressed in millimeters of the nominal inner diameter, but separated from the dimension series by a “/”. For example, the self-aligning roller bearing 230/500 represents an inner diameter of 500mm. The summary of the inner diameter code representation methods and examples is shown in the figure.

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