a variable device for regulating the outlet pressure of a fluid from a valve body , includes a pressure - sensing chamber having a wall formed by a resilient self - restoring diaphragm which is responsive to pressure in the chamber . a valve element connected to the diaphragm controls flow into the chamber . increased pressure in the chamber decreases the flow into the chamber and decreasing pressure increases flow whereby fluid flow out from the chamber is maintained at a desired pressure . the outlet pressure is adjusted by deflecting the diaphragm in a direction to open the valve while permitting a section of the diaphragm connected to the valve member to remain responsive to the pressure in the chamber . an adjustment cover is provided to adjustably deflect the diaphragm and includes a catch mechanism to allow adjustment of the fluid outlet pressures and also retain the device at a desired value . an indicator arrangement may be provided to visually indicate the fluid outlet pressure .