Flat Oval Spiral Duct View the under online video to see the installation of oval duct and fittings. See that the reducer being used is undersized on its collar allowing for the oval duct to slip in excess of the collar. They are really making use of Unistrut with threaded https://round-conduit78900.liberty-blog.com/36835599/the-5-second-trick-for-round-conduit