Only works with ventless product, not with direct vent sealed glass units. 14D0468 Monessen Hearth Replacement SIT 820 NOVA Vent Free Fireplace Propane Gas Valve Model 0820636. This is a millivolt valve. Uses a thermopile (main valve), and thermocouple (pilot). Has 3/8" female pipe thread inlet and outlet connections. You can vary hi - lo flame height. Millivolt valves can be controlled by a switch, remote control, or thermostat. This is used by Monessen, Majestic, Empire, and many other fireplace companies.