The Flue Guard Woodstove Probe Thermometer combines the best features of both the ChimGard and the Flue-Gas thermometers. Autumn colors on the face specify the temperature and three stove operation zones, measuring the temperatures up to 1700 degrees Fahrenheit. The Flue Guard requires you to drill a 1/4 inch hole in your fluepipe. For double-wall stovepipe, drill a 1/4 inch hole in the outer wall and a 3/16 inch hole through the inner wall. Note: This item is made in the USA.