These Direct-Temp vent pipes are made by Selkirk. The gas pipe is specially designed to also work efficiently with corn and pellet appliances. The outer wall is make out of heavy duty galvanized steel and the inner wall is make from corrosion resistant 304 alloy stainless steel. The connections are make from leak proof fiberglass and silicone. The joints have gaskets and require no sealant. The vent pipes are available in five lengths and have a lifetime warranty.