The retainer, also referred to as the cage or separator, is used to separate and position the balls at equal intervals around the bearing raceways. Retainers are available in two standard types, according to the size and design of the bearing itself. The most common is a 2-piece closed ball pocket design known as a ribbon retainer. The crown retainer is a single piece open ball pocket design. For most bearing sizes, the retainer type is as shown in the individual bearing tables, and cannot be specified by the user 

Ball Bearing Cage, also referred to as the bearing retainer or the bearing separator, is used to separate and position the balls at equal intervals around the bearing raceways. Retainers are available in two standard types, according to the size and design of the bearing itself. The material used is 300 series stainless steel