Versions 0110DOW, 0120DOW, 0110GOW and 0120GOW are "outside of wall or ground" integral sleeve static curtain kind fireplace dampers.  Model 0110GOW and 0120GOW are specifically made for source or return ducts that terminate at a grille or sign up. Design 0110DOW and 0120DOW are made for by penetrations (ductwork linked https://finnfxlzn.blogvivi.com/37722584/the-definitive-guide-to-dampers-for-industrial-sector