Product D0110DOW, D0120DOW, D0110GOW, D0120GOW are "away from wall or floor" integral sleeve dynamic curtain type fireplace dampers. Design D0110GOW and D0120GOW are designed for offer or return ducts that terminate at a grille or sign up. Design D0110DOW and D0120DOW are designed for by penetrations (ductwork connected to either side) https://sergiogxpdr.creacionblog.com/36708189/the-definitive-guide-to-heavy-duty-stainless-steel-damper-manufacturers