Designed for appliances tested and listed for use with wood stoves, fireplaces, furnaces, boilers, stoves, ranges, water heaters, or other appliances fueled by wood, oil, coal, or gas. 6", 9", and 12" chimney pipe has 1" insulation blanket; 24", 36" chimney pipe has 1⁄2" insulation. To calculate the installed length of DuraPlus chimney pipe, subtract 1 1⁄2" from each length of chimney pipe.