In both of these embodiments preferably the retaining means includes a plurality of projections projecting axially around the perimeter of one or both of the ends of the cylindrical sleeve and the cylindrical insert includes a plurality of apertures equal in number to {HEAD ~ the projections} located on {TAIL ~ the surface} of one or both of the flanges and located in positions such that the projections fit into the apertures 
located on
In both of these embodiments preferably the retaining means includes a plurality of projections projecting axially around the perimeter of one or both of the ends of the cylindrical sleeve and the cylindrical insert includes a plurality of apertures equal in number to { HEAD ~ the projections } located on { TAIL ~ the surface } of one or both of the flanges and located in positions such that the projections fit into the apertures
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