Styles 0110DOW, 0120DOW, 0110GOW and 0120GOW are "out of wall or flooring" integral sleeve static curtain type hearth dampers.  Design 0110GOW and 0120GOW are particularly made for offer or return ducts that terminate in a grille or register. Design 0110DOW and 0120DOW are suitable for via penetrations (ductwork linked to https://dampers-for-industrial-se45677.pointblog.net/top-latest-five-heavy-duty-stainless-steel-damper-manufacturers-urban-news-83561010