Diameter: 8". Construction Material: Inner wall of .020" 430 stainless steel, Outer wall .021" Galvalume steel. Clearance: 2" clearance to combustibles. Listings: c-UL-us Listed to UL 103 and ULC S604 (MH7399). Painted Black. Factory installed twist-lock fittings. The DuraTech Square Ceiling Support Box supports chimney pipe and provides a positive connection between the support box and the chimney pipe with a built-in twist lock feature. This ceiling support is suitable for both flat and cathedral ceiling applications and it can also be used in short attic spaces. Designed for appliances that are tested and listed for use with a 2100 degrees F HT chimney system, such as woodstoves, fireplaces, furnaces, boilers, stoves, ranges, water heaters, or other appliances fueled by wood, oil, coal, or gas. This Ceiling support fits between 16" on center joists and most mobile home applications and supports up to 60' of DuraTech Chimney. A 2" wide trim collar is included. DuraTech is a double-wall, all-fuel chimney system for use with wood stoves, fireplaces, furnaces, boilers, ranges, water heaters, or other appliances fueled by wood, oil, coal, or gas, and zero-clearance fireplaces that are factory-built.