DuraVent 4BVF 4'' Dia. Inner Aluminum Adjustable Roof Flashing Vent Roof Flashings are used to weatherproof vent terminations on roofs. Flashing is designed to prevent water entrance when a hole must be cut in your roof. This Aluminum Adjustable Roof Flashing with 4 Inch Inner Diameter from the Round Gas Vent series is a Type B gas component and consists of the duralock system for a tight seal. Use to weather proof the penetration of vent pipe through the roof. Storm Collar required. Select roof flashing based on pitch of roof. For pitches of 0/12 6/12. Made of galvalume. Features. Double Wall Construction. UL ListedSpecifications. Collection Round Gas Vent. Inner Pipe Gauge 28. Length 17. Outer Pipe Gauge 28. Pipe Inside Diameter 4. Width 17. Configuration Flashing. Inner Pipe Material Aluminum. Material Aluminum. Outer Pipe Material Galvanized Steel. Pipe Class Type B. Pipe Shape Round. Fuel Type Gas. Approved for Commercial Use No. Certifications UL