The guide bush for a reciprocating rod fits in a wall aperture and is of elastic material. It has at one end an annular groove adjacent to a collar (1), by which it is secured in the wall. On the side furthest from the collar the groove has a conical face forming transition into a cylindrical end portion. On the collar side there is a membrane (10) with a central bore smaller than the rod diameter, while ribs (9) running in the longitudinal direction protrude from the bush inner surface and form guides for the bar. There can be three pairs of ribs, evenly spaced round the periphery and tapering towards the collar.
