Pressure Reducing and Pressure Sustaining Hydraulic Control Valves are advanced hydraulic valves with dual pilot control that reduce the outlet pressure to the desired level while maintaining the inlet pressure constant. The first of the two pilot systems on the valve is the upstream pressure stabilising pilot and stabilises the inlet pressure. The other pilot is the pressure reducing pilot and reduces the outlet pressure to the value determined by the user and keeps it constant. In this way, the system is protected from sudden pressure fluctuations and safe working conditions are provided. Excessive flow and high pressure that may occur in downward sloping lines are reduced by the valve and the system is guaranteed to operate at normal values. This valve, which keeps the inlet and outlet pressure under constant control without being affected by changes in the amount of flow, offers long-lasting, reliable and precise pressure management.