7" x 48" Duravent DuraTech Factory-Built Double-Wall Galvalume Chimney Pipe 7DT-48 DuraVent DuraTech 7" Galvalume 48" Chimney Pipe is designed for appliances that are tested and listed for use with a 2100 °F HT chimney system such as wood stoves fireplaces furnaces boilers ranges water heaters or other appliances fueled by wood oil coal or gas. Diameter: 7" Length: 48" Galvalume Can be used for wood stoves fireplaces furnaces boilers ranges water heaters or other appliances fueled by wood oil coal or gas. Thermal Tech insulation 10â€-24†diameter pipes feature an .027†430 stainless steel inner wall and an outer wall of .029†galvalume or .027†430 stainless steel. A Refractory insulation is encased between walls. Only stainless pipes use the stainless end rings. Regular galvalume pipe uses galvalume end rings.