Goes along with the inner flange and internal locking band (with centering extension). The outer locking band is on the outside for more assistance, which makes it a more robust procedure. Reduction in cross-area: The inner dimensions (width and peak for rectangular ducts, diameter for round ducts) with the smoke https://grease-tight-extract-duct34556.blue-blogs.com/44460171/grease-tight-extract-ductwork-for-dummies