The HAHN clean cap is a retrofit item. It protects the piston rod seal by removing dirt from the rod as it plunges into the housing, thereby preventing the intrusion of foreign matter to the inside of the gas spring. It consists of an aluminum disk with a rubber wiper and a plastic cap, which is placed over the gas spring, holding the disk and wiper in position. Applying this retrofit wiper precludes the use of the standard protection tube and the standard safety lock. The HAHN clean cap is often used in construction machines to prevent the intrusion of dust, sand, etc. into the gas spring. Caution: employing the HAHN clean cap results in stroke and force losses (friction). The amount of force loss is dependent upon the ambient temperature and the actuation frequency.