Louver Damper Adjustable 18H x 42W

20.5 In.H 44.5 In.W Drnbl Extrd Alu Combo Dmpr Louver Type Combination Frame Type Flanged Outside Height 17 1/2 in Outside Width 41 1/2 in Rough Opening Height 18 in Rough Opening Width 42 in Louver Maximum Intake 2 025 cfm Maximum Exhaust 2 896 cfm Flange Width 1 1/2 in Free Area 1.8 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 39 3/4 in Number of Blades 3