20 india Nrm Opn Rnd Stel Zone Cntrl Dampr For Nominal Duct Diameter 20 in Damper Application Motorized Number of Panels Not Applicable Overall Height 4 5/8 in Overall Length 4 7/8 in Rough Opening Shape Round For Duct Shape Round Overall Width 20 in Frame Material Thickness Not Applicable Blade Material Galvanized Steel Maximum Air Pressure 0.5 in wc Overall Diameter 20 in Rough Opening Length 20 in Rough Opening Width 20 in Damper Type Dynamic