Relief valves prevent damage in case of over-pressurization. Baked enamel finish for increased corrosion resistance Collar threads enable easy fixturing (except RRH-1001 and RRH-1508) Double-acting version for fast retraction. Nickel-plated, floating center tube increases product life. Hollow plunger allows for both pull and push forces. CR-400 couplers and dust caps included on all models. Plunger wiper reduces contamination, extending cylinder life. Smooth hollow saddles are standard on allmore RRH-models. less