There are two basic types of miniature and instrumental ball bearings: deep groove ball bearings and angular contact ball bearings.Deep groove ball bearings can be further divided into following five types according to the detailed design:The standard form,The flanged outer ring type, the extended inner ring type, the extended type which the radial thickness of the outer or inner ring is much wider than ordinary bearings, the thin type which both the inner and outer radials are very thin.Deep groove ball bearings can also be classified into "open type", "dust cover type" and "sealing circle type" according to the form of sealing or dust proof.