Louver Damper Adjustable 18H x 30W

20.5 In.H 32.5 In.W Drnbl Extrd Alu Combo Dmpr Louver Type Combination Frame Type Flanged Outside Height 17 1/2 in Outside Width 29 1/2 in Rough Opening Height 18 in Rough Opening Width 30 in Louver Maximum Intake 1 402 cfm Maximum Exhaust 2 005 cfm Flange Width 1 1/2 in Free Area 1.3 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 27 3/4 in Number of Blades 3