Model D0110DOW, D0120DOW, D0110GOW, D0120GOW are "outside of wall or flooring" integral sleeve dynamic curtain type hearth dampers. Model D0110GOW and D0120GOW are created for offer or return ducts that terminate in a grille or register. Model D0110DOW and D0120DOW are suitable for through penetrations (ductwork linked to either side) exactly https://heavy-duty-stainless-stee90011.buyoutblog.com/36937191/the-heavy-duty-stainless-steel-damper-manufacturers-diaries