Rolling elements for bearings include balls, needles, rollers.
All these rolling elements are made of hardened bearing steel and depending on the application are delivered in different accuracy classes with different dimensional and shape deviations.
Balls of one dimension and a certain accuracy class are selected into groups with very narrow diameter tolerances. Each selection group is packed separately and the group's average deviation is given on the packaging. For each accuracy class, the greatest and smallest permissible deviation as well as shape deviation are determined.