6" DuraVent DuraPlus Flat Ceiling Support Box 6DP-FCS This flat ceiling support box supports the chimney pipe and provides a positive connection between support box and chimney with a built-in twist-lock. Designed for installation in flat ceilings only. Supports up to 35' of DuraPlus chimney pipe. Use adaptor to attach DVL or DuraBlack to the support box. A 2" wide trim collar is included. Not painted but can be painted with high temperature paint. Use when air-cooled chimney is required Free-floating inner 430-alloy liner maintains structural integrity in chimney fires 2" clearance to combustibles Outer diameter is 4" larger than inner diameter Triple-wall chimney For uses with wood stoves fireplaces furnaces boilers stoves ranges water heaters or other appliances fueled by wood oil coal or gas Clean smooth exterior finish .016” 430 stainless steel outer wall or .018” galvanized steel outer wall. .018” aluminized steel intermediate liner. .016” 430 stainless steel inner liner. Insulated layers plus ventilated air space. Locks tightly with a precision twist-lock connection.