4" Type B Gas Vent 90-Degree Adjustable Elbow 4GVL90 This adjustable elbow offsets obstructions as needed. Elbow swivels 360 ° at base. Adjustable from 0 to 90 degrees. Elbow must be supported when installed. 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