The hydraulic Piston Seal is an element of a hydraulic jack that aids in stopping the hydraulic fluid from leaking out of the jack cylinder. The seal is often made of a resilient and flexible substance, such as rubber or polyurethane, and is made to snugly fit around the jack piston rod. The piston moves higher and lifts the load when the Hydraulic Piston Seal is in use because hydraulic fluid is poured into the cylinder.