Models 0110DOW, 0120DOW, 0110GOW and 0120GOW are "outside of wall or flooring" integral sleeve static curtain style fireplace dampers.  Model 0110GOW and 0120GOW are specifically created for source or return ducts that terminate at a grille or register. Design 0110DOW and 0120DOW are suitable for by penetrations (ductwork connected to https://cristianauiwk.blogsuperapp.com/37542264/details-fiction-and-heavy-duty-stainless-steel-damper-manufacturers