Goes along with the internal flange and internal locking band (with centering extension). The outer locking band is on the surface for more aid, making it a more robust program. Reduction in cross-section: The inner dimensions (width and height for rectangular ducts, diameter for circular ducts) of your smoke extracting https://fire-resisting-ductwork-i78900.slypage.com/37491549/not-known-factual-statements-about-grease-tight-extract-ductwork