Class DV pipe is a direct vent or balanced flue venting system capable of handling the exhaust from appliances that burn propane & natural gas. The inner core pipe vents the exhaust gases while the outer pipe carries fresh air from outside to the appliance. So there is essentially a 2 way street of incoming and outgoing traffic. These are most commonly found on gas fireplaces & stoves. Despite the double wall construction the outside shell of this pipe still gets hot and requires an air space. The metal used on the outside is galvanized steel and the metal used on the inside is aluminum. Lengths range from 6″ to 60″ and diameters range from combinations of 3″/5″, 4″/7″, 5″/8″, to 8″/11″. We supply & install these products.