Hydraulic Seals prevent leakage of fluid from within the cylinder to the outside. This allows pressure build up on one side of the piston, making the Cylinder extend or retract. Wear rings guide the piston and piston rod within the hydraulic cylinder, absorbing transverse forces, preventing metal-to-metal contact. Scrapers or Wipers scrape dirt, foreign particles, chips or moisture from the piston rods as they retract into the cylinder, preventing contamination.