A simple and good packing for a piston can be obtained by using three leathers. One, at the centre, is a simple disc, and on each side of it is a cup leather that tits the bore of the pump barrel. One of the cup leathers is placed against the end of the plunger, and the other is kept in place by a thick washer, a set-screw passing through the centre of the leathers and threading into the plunger. The whole is pulled up tight by means of a nut bearing on the face of the washer.