Versions 0110DOW, 0120DOW, 0110GOW and 0120GOW are "outside of wall or floor" integral sleeve static curtain sort hearth dampers.  Product 0110GOW and 0120GOW are precisely designed for supply or return ducts that terminate at a grille or register. Product 0110DOW and 0120DOW are made for by way of penetrations (ductwork https://dampers-for-industrial-se45667.blue-blogs.com/44619784/the-2-minute-rule-for-dampers-for-industrial-sector