This Imperial 10-in Duct Board Starting Collar provides a reliable transition from a flat surface to round pipe or insulated flexible duct. Used with duct board or a plenum, this versatile starting collar features extra-long tabs to fit most R6 duct board thicknesses through 1-1/2-in. The collar is easy to install with sheet metal screws for a secure fit (screws sold separately). It is made from 30-gauge galvanized steel for rust resistance and lasting durability, and is suitable for use in most heating, venting and air conditioning applications.