Types 0110DOW, 0120DOW, 0110GOW and 0120GOW are "out of wall or flooring" integral sleeve static curtain style hearth dampers.  Design 0110GOW and 0120GOW are particularly created for source or return ducts that terminate at a grille or sign-up. Product 0110DOW and 0120DOW are designed for by means of penetrations (ductwork https://emiliotlcqe.wizzardsblog.com/37005637/the-basic-principles-of-dampers-for-industrial-sector