Design D0110DOW, D0120DOW, D0110GOW, D0120GOW are "away from wall or floor" integral sleeve dynamic curtain sort fire dampers. Design D0110GOW and D0120GOW are made for source or return ducts that terminate in a grille or sign up. Model D0110DOW and D0120DOW are designed for through penetrations (ductwork connected to either side) https://dampersforindustrialsecto45666.anchor-blog.com/17259855/dampers-for-industrial-sector-fundamentals-explained