A single-acting piston seal is designed for cylinders where pressure is applied from one side only.

Rod and buffer seals maintain sealing contact in sliding motion between the cylinder head and the piston rod.

Wiper seals maintain sealing contact to the piston rod when the equipment is stationary (static, no reciprocating motion of rod) and in use (dynamic, reciprocating rod), whereas the tolerance for the rod diameter d is determined by the rod seal.