To differentiate the quality of bearings, the ABEC classes were introduced. The higher the ABEC rating, the more precise the manufacturing tolerances were maintained during production.
The classification of ball bearings into "ABEC3", "ABEC5", or "ABEC7" is often mistakenly regarded as the key quality criterion. However, the term "ABEC" (Annular Bearing Engineers Committee) simply refers to an agreement regarding manufacturing tolerances and not the "overall quality" of a bearing.
The "ABEC" designation, along with several other geometric measurement accuracies, also specifies the maximum allowable height and lateral play (runout) of a ball bearing. For example, the difference between an "ABEC5" and an "ABEC7" bearing in terms of height runout is just a tiny 0.002 millimeters. While high precision certainly contributes to very smooth running properties, these minute differences are relatively insignificant in real-world use, as the "installation environment" generally has much higher tolerances.