Styles 0110DOW, 0120DOW, 0110GOW and 0120GOW are "out of wall or flooring" integral sleeve static curtain type hearth dampers.  Product 0110GOW and 0120GOW are specifically created for source or return ducts that terminate at a grille or sign-up. Design 0110DOW and 0120DOW are suitable for by way of penetrations (ductwork https://dampers-for-industrial-se12233.blogdal.com/37579263/everything-about-dampers-for-industrial-sector