These bearings have a slightly shallower groove in the inner ring than deep groove ball bearings, and the inner diameter of the non-flanged side of the outer ring extends from the bottom of the groove in a cylindrical shape, allowing the outer ring to be separated and facilitating bearing installation. Typically, two bearings are used in opposition. These are small bearings with inner diameters ranging from 4-20mm, mainly used in small generators, gyroscopes, measuring instruments, etc. Generally, copper alloy stamped cages are used.