Designs 0110DOW, 0120DOW, 0110GOW and 0120GOW are "out of wall or floor" integral sleeve static curtain variety fire dampers.  Product 0110GOW and 0120GOW are specially suitable for supply or return ducts that terminate at a grille or register. Product 0110DOW and 0120DOW are created for as a result of penetrations https://dampers-for-industrial-se23455.estate-blog.com/36005528/an-unbiased-view-of-dampers-for-industrial-sector