The BASO Q90FF-3 Pilot Assembly/Sensor. It integrates a flame sensor and a pilot assembly into a single device and is constructed of metal for durability,An essential dual-purpose part for gas-fired HVAC systems, including boilers and furnaces, . While the flame sensor detects the presence of a flame to ensure safe operation, the pilot assembly ignites the gas burner during starting. https://www.partshnc.com/q90ff-3-baso-gas-products-pilot-assysensor-27-cbl-032