DuraVent 9607GACF Galvanized Steel 48 Inch Chimney Pipe - 8 Inch Inner Diameter Class A systems are used for high-temperature exhaust gases from common solid fuels such as: Wood, Coal, Oil, and other high-output fuels. With a thermal Tech Blanket insulation encased between dual walls. DuraTech offers the optimum in safety and performance. It keeps the outer wall of the chimney cool, while ensuring high flue gas temperatures for optimum draft performance. Designed for appliances that are tested and listed for use with 2100 degree fahrenheit HT chimney systems.