Heatilator Heatnglo Direct Vent Fireplace 27" Thermocouple replaces Robertshaw 446-511 Thermocouple for Direct Vent Fireplaces Replaces ( replacement for) Robertshaw 446-511 Fits Robertshaw & some SIT 820 NOVA Gas Valves with fine thread. works on many fireplaces part numbers 34820 446-511 72956