These sets of four matched super-precision angular contact ball bearings are available as universally matchable bearings or in preconfigured arrangements. Sets of four bearings arranged in tandem need to be mounted against a single bearing, or a set of bearings in tandem, to achieve the desired preload. All the other arrangements are available in different preload classes and correct mounting results in preload within a predetermined range, without the need for shims or similar devices. The bore and outside diameters of the bearings are matched to within a maximum of one-third of the permitted diameter tolerance, to provide better load distribution than single universally matchable bearings.