Goes along with the inner flange and interior locking band (with centering extension). The outer locking band is on the outside for more guidance, making it a more robust process. Grease duct is either routed by way of a fire rated shaft enclosure or wrapped with an permitted fire insulating https://grease-tight-extract-duct23344.bloggazzo.com/35766072/detailed-notes-on-grease-tight-extract-ductwork