Types 0110DOW, 0120DOW, 0110GOW and 0120GOW are "out of wall or floor" integral sleeve static curtain form fire dampers.  Model 0110GOW and 0120GOW are exclusively designed for provide or return ducts that terminate in a grille or register. Product 0110DOW and 0120DOW are designed for by means of penetrations (ductwork https://remingtoncukym.yomoblog.com/43864807/the-heavy-duty-stainless-steel-damper-manufacturers-diaries