The single row deep groove ball bearing is the most popular type of rolling bearing. Because the inner and outer raceway radii are only slightly larger than the ball diameter, it has considerable axial load carrying capacity in either direction, as well as radial loading. They are suitable for high speeds and can be supplied with shields or seals. The shielded type have a running clearance between the inner-race and the metal shield, whereas the seals (made from synthetic rubber), make contact with the inner race. Both shielded and sealed bearings are supplied with the correct amount of lithium base grease.