Flat Oval Spiral Duct Look at the below online video to see the installation of oval duct and fittings. Notice that the reducer getting used is undersized on its collar enabling the oval duct to slide in excess of the collar. They can be utilizing Unistrut with threaded rods as https://round-conduit02233.laowaiblog.com/35508292/the-definitive-guide-to-oval-conduit