The Duravent Flat Ceiling Support Box provides a high quality support for your Duratech Chimney system and an integrated flue extension for tight installations. This support box is suitable for flat ceilings only. It fits between standard 16-inch on center joists and most manufactured home applications. With various sizes to choose from so that each unit provides a positive connection between support box and chimney with a built-in twist-lock. With the strength to support up to 60 feet of DuraTech Chimney, the integrated flue extension accepts single or double-wall stovepipe that will connect directly to the ceiling support without the need of a separate chimney adaptor. DuraTech is a double-wall chimney system for use with wood stoves, fireplaces, furnaces, boilers, ranges, water heaters, or other appliances fueled by wood. DuraTech is designed for normal, continuous operation at 1,000 degree flue gas temps. NOTE: Venting components should be installed by a licensed installer in accordance with local codes and within the manufacturer's specified guidelines as noted in your appliance's installation manual.