· DuraVent"s type B gas vent system, use with natural gas· 1 in. Clearance to combustibles in single and multi-family dwellings· Adjustable roof flashing used to weather-proof the penetration of vent pipe through the roof, storm collar· Select roof flashing based on pitch of roof for pitches of 0/12 thru 6/12 in.· 6-3/4 in. Dia. holeSpecifications