Model D0110DOW, D0120DOW, D0110GOW, D0120GOW are "away from wall or ground" integral sleeve dynamic curtain variety fire dampers. Product D0110GOW and D0120GOW are designed for source or return ducts that terminate at a grille or sign up. Model D0110DOW and D0120DOW are created for via penetrations (ductwork linked to both sides) https://collinsldti.blogacep.com/42352166/dampers-for-industrial-sector-for-dummies