PLAIN BEARINGS, PLAIN BEARINGS WITH SURROUNDING GROOVES SPACED ONE BEHIND THE OTHER IN THE LONGITUDINAL DIRECTION OF THE BEARING BORE; PLAIN BEARINGS WITH RINGS OF DIFFERENT BEARING MATERIAL SPACED ONE BEHIND THE OTHER IN THE LONGITUDINAL DIRECTION OF THE BEARING BORE; PARTS OF THE AFOREMENTIONED BEARINGS; ALL THE AFOREMENTIONED PLAIN BEARINGS FOR MEDIUM-TO HIGH-SPEED INTERNAL COMBUSTION ENGINES