6" Type B Gas Vent Galvalume Tall Cone Roof Flashing for Flat Roofs 6GVFF This roof flashing is used to weatherproof the penetration of vent pipe through the roof. Storm Collar required. Use on flat roofs chase enclosures or masonry chimney. 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