Flat Oval Spiral Duct View the below online video to begin to see the installation of oval duct and fittings. Recognize the reducer being used is undersized on its collar enabling the oval duct to slip in excess of the collar. They can be using Unistrut with threaded rods as https://oval-conduit80011.mdkblog.com/42531177/new-step-by-step-map-for-round-conduit