Designed for use on one piece pistons, the five part assembly consists of an endless precision rubber moulded sealing element supported at each end with angle split support rings. The support rings are designed to accommodate split Polyacetal anti-extrusion bearing rings. The design allows the anti extrusion bearing rings to react positively to increasing pressures. The final assembly provides a robust sealing unit designed to operate at higher pressures. The seal is also suitable for existing two piece pistons of the same housing dimensions.