3" Type B Gas Vent Galvalume Adjustable 0/12 - 6/12 Pitch Flashing 3GVF Use this roof flashing to weatherproof 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. For Category 1 gas appliances 1" clearance to combustibles Easy-fit twist-lock design with no fitting hassles 0.012" aluminum inner 0.018" galvanized outer