4" DuraVent DirectVent Pro Aluminum Adjustable 0/12-6/12 Roof Flashing 46DVA-F6DS This roof flashing is used to weather-proof the penetration of vent pipe through the roof. Storm collar required. Used for metal or tile roofs. Provides combustion air and exhaust venting for gas appliances Clearance to combustibles mandated by appliance listing The components twist-lock together for a quick secure fastener-free installation 0.020" aluminum inner 0.018" steel outer Offsets venting obstructions .020†aluminum inner wall .018†galvanized steel outer wall Painted outer walls made of laser welded .018†galvalume steel. Caps also available in stainless steel and copper. Outer pipe brings combustion air to the appliance. Inner pipe exhausts flue gases to the outside. Gaskets or sealants not required (unless specified by the appliance manufacturer).