The single-stage FM pressure regulators, in their application in oxygen, are suitable for direct mounting on oxygen cylinders. They are produced with oxygen cylinder connection fitting in the different reference standards of the destination Countries and with a direct connection to a Rs series variable area flowmeter. This is supplied in some options regarding the scale reading values and the outlet threads, suitable to connect a humidifier or a simple hose connector. The FM pressure regulators are designed for use with preset outlet pressure value. The structure and the fittings are in brass and the pressure relief valve is pre-calibrated, to guarantee protection in case of any system failure. A protective silicone cover prevents gauge damages caused by possible shocks received during transport or use.