Louver Damper Adjustable 36H x 18W

38.5 In.H 20.5 In.W Drnbl Extrd Alu Combo Dmpr Louver Type Combination Frame Type Flanged Outside Height 35 1/2 in Outside Width 17 1/2 in Rough Opening Height 36 in Rough Opening Width 18 in Louver Maximum Intake 1 929 cfm Maximum Exhaust 2 758 cfm Flange Width 1 1/2 in Free Area 1.7 sq ft Beginning Point of Water Penetration 1 118 fpm Maximum Air Velocity 3 000 fpm Blade Angle 45 Degrees Material Aluminum Inside Height 34 1/2 in Inside Width 15 3/4 in Number of Blades 7