FOR DOUBLE WALL STOVE PIPE - Allows for accurate temperature measurement inside double wall flue pipes. BRIGHTLY COLORED TEMPERATURE ZONES - Easy to Read, optimize efficiency, prevent overheating, minimize creosote. 4 INCH LONG PROBE - Accurately monitors wood stove temperature up to 1700F. Chrome plated to resist corrosion. EASY INSTALLATION - Requires drilling a small hole, includes instructions, magnetically secured. MADE IN USA - High quality materials and construction. The Midwest Hearth flue pipe probe thermometer allows accurate temperature readings on wood stove chimneys that utilize double wall (insulated) chimney pipes. The 4" long probe extends through the outer and inner pipe walls to access temperatures from inside the center of the pipe where hot chimney gasses flow. The Midwest Hearth thermometer requires drilling a small hole (instructions included) and secures in place with a strong magnet. Bright high temperature paint offers quick easy-to-read temperature zones and resists fading from the high temperatures of a wood burning appliance. Steel construction and a chrome plated copper probe resists corrosion and delivers the quality construction you expect from an American Made product!