Product D0110DOW, D0120DOW, D0110GOW, D0120GOW are "out of wall or floor" integral sleeve dynamic curtain style hearth dampers. Design D0110GOW and D0120GOW are designed for offer or return ducts that terminate in a grille or sign up. Design D0110DOW and D0120DOW are suitable for via penetrations (ductwork linked to each side) https://dampersforindustrialsecto67789.thechapblog.com/35942158/considerations-to-know-about-heavy-duty-stainless-steel-damper-manufacturers