Models 0110DOW, 0120DOW, 0110GOW and 0120GOW are "outside of wall or ground" integral sleeve static curtain sort hearth dampers.  Design 0110GOW and 0120GOW are specially designed for supply or return ducts that terminate in a grille or register. Product 0110DOW and 0120DOW are made for via penetrations (ductwork linked to https://heavydutystainlesssteelda12233.anchor-blog.com/17374987/heavy-duty-stainless-steel-damper-manufacturers-can-be-fun-for-anyone