Since the seal had to be both interior and exterior, each piston was made up of from 3 to 5 parts, which meant high stocks along with and fitting problems, quite apart from being of mediocre efficiency under pressures of 10 to 20 bars.
The type of piston produced by PAULSTRA consists of only one piece of stamped steel on to which are bonded 2 sealing lips. The shape of these lips is adapted to ensure a good seal with little friction and to avoid extrusion.