Pneumatic seals stop air or other gaseous material escaping a cylinder or another pneumatic device; they also exclude extraneous substances from getting into the housing. Made of a variety of materials, including Polyurethane, Nitrile, Viton, Silicone, EPDM and PTFE, they are designed for low operating pressures, they can used in both rotary as well as reciprocating motions.
They may be single or double-acting. Single-acting seals act in one axial direction only. Double-acting seals as the name suggests, act in both directions for reciprocating motion.