Types 0110DOW, 0120DOW, 0110GOW and 0120GOW are "outside of wall or flooring" integral sleeve static curtain style hearth dampers.  Model 0110GOW and 0120GOW are specially designed for source or return ducts that terminate in a grille or sign up. Model 0110DOW and 0120DOW are designed for via penetrations (ductwork connected https://dampersforindustrialsecto03344.theisblog.com/37321196/heavy-duty-stainless-steel-damper-manufacturers-an-overview