The DuraTech Stainless Steel Wall Thimble Cover goes over the exterior side of the Wall Thimble, providing a sleek, clean finish. 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. Thimble not included.