DuraTech chimney pipe is designed for appliances that are tested and listed for use with a 2100 Degree F HT chimney system, such as woodstoves, fireplaces, furnaces, boilers, stoves, ranges, water heaters, or other appliances fueled by wood, oil, coal, or gas. The DuraTech chimney System is designed to stay cool on the outside and provide a hot draft on the inside. A fire-safe design protects both the chimney and the building. To calculate installed length of 5″, 6″, 7″, or 8″ DuraTech Chimney, subtract 1 +” from each joint overlap of chimney pipe. DuraTech’s Light-weight insulation and sleek 1″ wall design, combined with twist-lock fittings, provides for easy installation. No locking bands or mechanical fasteners required.