Self-Operated Pressure Reducing Gas Regulator, High Inlet Pressure; 3/4″ - 2″ (DN20 - DN50) The Mark 627 Series is a self-operated, pressure -reducing regulator and is designed to provide tight-shutoff and accurate regulation on low or high pressure systems. This spring loaded pressure regulator can be used on air, natural gas or a variety of other gases. The top entry design allows for easy in-line maintenance.