Single acting fluid seals (SAFS) are commonly used in stage cylinders for truck box hoists. SAFS are often used with anti-extrusion rings either on ID or OD depending on rod seal or piston seal. Fluid seals can also be used with a wear ring where side loads could be a concern. Double acting fluid seals (DAFS) are composed of three, four, or five pieces. The seal element is usually Nitrile and can be stretched onto the solid piston head while the wear rings and anit-extrusion rings are split for ease of installation.