The most common standardized ball bearing size is the 608 series. The 608 series is the original standard ball bearing. In the 608 series, the ball bearing typically consists of optional closures, inner race, outer race, balls, and a ball retainer.
The ABEC rating is graded in five tiers of 1, 3, 5, 7, and 9 ratings, where the higher the rating, the tighter the tolerances of the bearing. Ball bearings that have a high ABEC system rating are used for high precision applications such as the aerospace industry or surgical equipment, and lower ABEC graded ball bearings are used for more everyday bearing applications. ABEC ratings also reflect the relative prices of ball bearings; the higher the grading, the more expensive the ball bearings.