The AR 503 model is characterized by the presence of 3 semi-hydraulic diaphragms in NBR, Desmoplan or Viton rubber, high pressure air chamber, seals in NBR or Viton rubber. All components that come into contact with liquids are made of plasticized aluminium. Furthermore, the sprayer pump has die-cast casings with mechanical gears in an oil bath, the tank is made of transparent plastic material for good visual control of the liquid level. In addition, it features an oil drain plug and segmented pistons for greater efficiency of the "oil cushion" system.