Piston Cup seals are used on rams or plungers in both hydraulic and pneumatic applications. To obtain the best results from any style of piston cup, it is recommended that the piston properly support the heel of the cup. Basic piston cup seals are typically used in low pressure pneumatic and hydraulic cylinders. Fabric reinforced piston cups are used in applications where tolerable pressures up to 800 psi can be sealed. Piston cups are useful in applications where large extrusion gaps exist.