Oval Spiral Duct is a single wall duct with a unique 4 ply locking seam creating wall stability. It is available in hundreds of sizes with minor axis from 5" to 24" and major axis from 13" to 81". For sizes beyond the range of manufactured spiral duct or alternative construction ECO Duct Products will provide Oval-Weld Duct with a longitudinal seam or continuous seam weld. Oval Spiral Duct is fabricated to SMACNA Duct Construction Standards or customer code