The cage has one or more side rings distorted in the radial direction and containing a bore surface. An annular portion (8) of the ring (2) supporting this surface (3) is joined to the main part of the cage by bending portions (7) distorting in the radial direction. The ring can have slot-type apertures (4,5) at intervals in the peripheral direction on pitch circles of different diameters, those on the one circle being offset in the peripheral direction from those on the other. Six or more pairs of bending portions can be provided.
