Louver Damper Adjustable 18H x 54W

20.5 In.H 56.5 In.W Drnbl Extrd Alu Combo Dmpr Louver Type Combination Frame Type Flanged Outside Height 17 1/2 in Outside Width 53 1/2 in Rough Opening Height 18 in Rough Opening Width 54 in Louver Maximum Intake 2 648 cfm Maximum Exhaust 3 787 cfm Flange Width 1 1/2 in Free Area 2.4 sq ft Beginning Point of Water Penetration 1 118 fpm Maximum Air Velocity 3 000 fpm Blade Angle 45 Degrees Material Aluminum Inside Height 16 1/2 in Inside Width 51 3/4 in Number of Blades 3