Product Features Self-centering function (prevention of slight off-center matters) Designed to suit smaller and shorter hubs (as there is only small difference in dimension between inner(d) and outer(D) diameters, as well as its surface pressure is low) – The most compact-designed series No movement while installed as the inner-ring is directly attached to hub surface Diverse material & finish options available (e.g. stainless steel body for vacuum area, electroless nickel plating etc.)