Types 0110DOW, 0120DOW, 0110GOW and 0120GOW are "out of wall or floor" integral sleeve static curtain form fire dampers.  Design 0110GOW and 0120GOW are specifically made for offer or return ducts that terminate in a grille or register. Design 0110DOW and 0120DOW are suitable for by means of penetrations (ductwork https://archerzqgvj.bloggactif.com/38464339/dampers-for-industrial-sector-secrets