Class A pipe is a chimney system capable of handling the exhaust from appliances that burn cord wood, pellets, coal, oil, propane, & natural gas with temperatures up to 1000 degrees continuous and operating under a natural draft. They are commonly called double wall, triple wall, or solid pack pipe. This is because manufactures use different engineering methods to achieve similar results. Regardless the outside shell of this pipe still gets hot and requires an air space. The metals used on the outside can be galvanized steel, 430 stainless steel, or 304 stainless steel. The metals used on the inside can be 430 stainless steel, 304 stainless steel, or 316 stainless steel. They all have different properties and you will need to align them with your objectives. Lengths range from 6″ to 60″ and diameters range from 5″ to 14″. We supply & install these products.