Flexible Aluminum Ducting. This Class 0, non-combustible duct is constructed of a special aluminum alloy that prevents corrosion and metal fatigue. Machine fabrication produces a continuous lock seam that permits the duct to be pulled open, compressed, bent, and re-bent without developing leakage. It can be used for concealed venting and eliminates the need for elbows. Various applications include dryer venting, air conditioning, fresh air intakes, heating, and exhausting