1. Universally Matched Bearings: Universally matched bearings are specially machined so that, when mounted close together, any combination can achieve the desired internal clearance or preload, as well as even load distribution, without the need for shims or similar devices.
Matched bearings are used when the load-carrying capacity of a single bearing is insufficient (using a tandem configuration) or when subjected to combined loads or axial loads acting in two directions (using a back-to-back or face-to-face configuration).
2. Basic Design Bearings (Not for Universal Matching), for Single Bearing Configurations: Basic design single-row angular contact ball bearings are primarily used in configurations where only one bearing is present in each position. Their width and protrusion are within standard tolerances. Therefore, they are not suitable for mounting two single-row angular contact ball bearings close together.