Abstract: A sealing bush unit for sealing a reciprocating machine part has an annular bush with an inner diameter exceeding an outer diameter of the reciprocating pump to form a radial gap therebetween, a radially outer surface arranged so that a working pressure acts upon the same and the bush radially displaces towards the reciprocating part, one flat end face facing toward a suction zone and providing an abutment for the sealing bush, and another end face facing toward a pressure zone, wherein a pressing ring is arranged adjacent to the other end face of the bush with axial play relative to a machine housing.