9 mm and a bore diameter Less than 10 mm are known asExtra-small ball bearings. Standard ball retainers (cages) are made from pressed steel. Machined cages are used in bearing operating atvery high speed or for large diameter bearings. Deep groove ball bearings with seals or shields are standardized. They contain proper amount of grease inadvance.

6217 Nachi Bearing Open C3 Japan 85x150x28 Ball Bearings