Designs 0110DOW, 0120DOW, 0110GOW and 0120GOW are "outside of wall or ground" integral sleeve static curtain variety fire dampers.  Model 0110GOW and 0120GOW are especially created for supply or return ducts that terminate in a grille or register. Product 0110DOW and 0120DOW are suitable for by penetrations (ductwork linked to https://dampersforindustrialsecto68899.p2blogs.com/35600325/indicators-on-dampers-for-industrial-sector-you-should-know