8 thereby assumes the axial side sealing with respect to the counter rotation disk 46 at the suction port 48 and simultaneously the axial bearing function so that here too the number of components and the occurring friction are minimized the rear side 50 of the impeller 8 opposite from the impeller blades 42 comprises a further annular sealing surface 52 which annularly surrounds the opening 54 for receiving the rotor shaft the sealing surface 52 bears on a seal 56 which surrounds the rotor shaft 10 in a stationary manner and seals the rotor space 28 in the inside of the can 14 towards the pump space in which the impeller 8 is arranged this seal 56 is held in its bearing on the sealing surface 52 by a spring effect the seal 56 ensures that contamination in the fluid which is delivered by the impeller 8 may penetrate into the rotor space 28 in the inside of the can 14 and there lead to undesired friction or contamination the counter rotation disk 46 is preferably likewise designed of hard metal or of ceramic the side 58 furthest from the impeller 8 is designed in a spherical manner not shown in fig1 and.