Duplex angular contact ball bearings can be combined in rows of two, three or four bearings to accommodate required specifications. The back-to-back duplex (DB) arrangement and the face-to-face duplex (DF) arrangement allow for the application of both radial loads and axial loads in both directions. The DB arrangement has a wide space between load points and can handle large moment loads. For this reason, this type of duplex arrangement is preferable for use on the main spindles of machine tools. NTN Angular Contact Ball Bearing, Round Bore, Series: ULTAGE® HTA, 55 mm Bore Dia, 90 mm Outside Dia, 2 Rows, 33 mm W, 40 °Contact, Open Closure, 64000 N, High Carbon Chrome Steel Bearing, Phenolic Cage, 10300 RPM Grease/13100 RPM Oil Maximum, -40 to 120 °C