Model D0110DOW, D0120DOW, D0110GOW, D0120GOW are "outside of wall or ground" integral sleeve dynamic curtain form fire dampers. Product D0110GOW and D0120GOW are designed for provide or return ducts that terminate in a grille or register. Design D0110DOW and D0120DOW are made for by penetrations (ductwork connected to each side) where https://heavy-duty-stainless-stee67889.thezenweb.com/helping-the-others-realize-the-advantages-of-heavy-duty-stainless-steel-damper-manufacturers-75034810