Duct flanges are constructed of steel for durability and are powder-coated to withstand rust in humid environments. These flanges are perfect for use with our line of Air Ducting, Light-Proof Black Ducting, Insulated Ducting, and Terra-Duct, as well as other standard-sized ducting. Duct flanges feature pre-drilled holes for attaching to sheetrock and plywood walls, and they include an additional steel ring and bolt set for connecting to sheet metal ductwork. The rounded edges make duct flanges easy and safe to work with and install.