Abstract: A piston for a piston-cylinder unit comprises a piston body having passages which connect two spaces in a cylinder on opposing sides of the piston. The passages are covered by at least one valve disk which is centered relative to a center of the piston by a centering sleeve. A spring element is arranged between the piston body and the centering sleeve. This spring element, when mounted, spaces the centering element from the piston body and accordingly displaces the useful range of the centering element until the piston is assembled in its entirety and every structural component part of the piston occupies its intended position.

Abstract: A process for manufacturing a molded piston ring for a piston in a piston-cylinder unit from a material which can be molded in a master mold. The surfaces of the piston in contact with the piston ring are provided with a separating agent which substantially prevents adhesive contact between the piston and piston ring. The piston is placed in the master mold including a shaping piece which at least partially contacts the circumferential surface of the piston. As a result of piston ring material being pressed in at the contact point or contact points of the shaping piece an expansion zone is formed at the piston which is free from the piston ring material.