Valves are necessary to control the pressure, flow rate and direction of the fluid. Hydraulic valves are made to a high standard of quality and robustness. The diagram shows a few of the vast range of Hydraulic valves available. We should remember always that hydraulic systems are high pressure systems and pneumatic systems are low pressure systems. Hydraulic valves are made of strong materials (e.g. steel) and are precision manufactured. Pneumatic valves are made from cheaper Materials (e.g. aluminum and polymer) and are cheaper to manufacture.