Example of NSK suffix code content DB Paired duplex (back-to-back) 7208ADBDBB Four-pair combination 7318ADBBDBD Three-row combination 7318ADBTDBTD Five-row combination 7318ADBTDDF Pair-duplex (in series) 7320ADFDFD Three-row combination 7320ADFDDFF Four-row combination 7320ADFFDFT Four-row combination 7320ADFTDT Paired duplex (face to face) 7320ADTDTD three-row combination 7320ADTDDTT three-row combination 7320ADTT universal combination In order to make the same type of bearing, no matter how the combination can achieve the set preload, and control the width difference between the front and the back during manufacture and make Equivalent, this is the universal combined bearing. At this time, in order to avoid misunderstanding the bearing installation direction and obtain the correct combination, a V-shaped mark is made on the outer diameter surface of the outer ring of a single bearing. The direction of the tip of the V-mark arrow indicates the direction of the axial load (contact angle) applied to the inner ring. Front width difference f u003d back width difference b Therefore, it is suitable for various combinations. Preload clearance: 2f Preload clearance: 2bDB Combined back width difference 2u003d2b (u003d2f ) can get the set preload DF combined front width difference 2u003d2f (u003d2b) can get the set The front width difference f of the preload DT combination u003d the rear width difference b, and there is no play between DTs as in the usual DT combination.