8" DuraVent DuraPlus Galvalume Wall Thimble 8DP-WT This wall thimble adjusts from a minimum of 4 1â„4†to a maximum of 7 1â„4â€wall thickness and fits between standard wall studs. To accommodate thicker walls the telescoping pieces can be extended up to 16†with a field-fabricated extension installed. Interior trim ring painted black. Must be installed with DuraPlus chimney pipe horizontally through the wall and extend a minimum of 2†into the room beyond the interior wall. 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.