Piston Cups are available in various shapes and compounds. The selection should be made on the basis of pressure, temperature and the type of air or fluid in which the cup must function. Buna-N and Cotton Duck Fabric are designed to handle moderate pressure cylinders up to 1500 PSI. Against air, water and petroleum base hydraulic fluids and lubricating oils. Neoprene piston cups (NP Series) are also available.