The Garland 4518817 is a 1980 Series thermocouple for Garland commercial cooking equipment. This 18-foot thermocouple, with a 20-30mV output, is a safety component that monitors pilot flames in gas-fired appliances. If the flame extinguishes, it signals the gas valve to shut off, preventing gas buildup. https://partsfe.ca/thermocouple-for-garland-part-4518817