Types 0110DOW, 0120DOW, 0110GOW and 0120GOW are "out of wall or flooring" integral sleeve static curtain style fireplace dampers.  Product 0110GOW and 0120GOW are particularly designed for provide or return ducts that terminate in a grille or sign up. Model 0110DOW and 0120DOW are designed for by way of penetrations https://heavy-duty-stainless-stee58912.mdkblog.com/43007110/the-5-second-trick-for-dampers-for-industrial-sector