Designs 0110DOW, 0120DOW, 0110GOW and 0120GOW are "outside of wall or floor" integral sleeve static curtain sort fire dampers.  Product 0110GOW and 0120GOW are specifically created for offer or return ducts that terminate at a grille or register. Design 0110DOW and 0120DOW are made for through penetrations (ductwork linked to https://dampersforindustrialsecto12344.blog-a-story.com/18039540/top-latest-five-heavy-duty-stainless-steel-damper-manufacturers-urban-news