Louver Damper Adjustable 48H x 18W

50.5 In.H 20.5 In.W Drnbl Extrd Alu Combo Dmpr Louver Type Combination Frame Type Flanged Outside Height 47 1/2 in Outside Width 17 1/2 in Rough Opening Height 48 in Rough Opening Width 18 in Louver Maximum Intake 2 671 cfm Maximum Exhaust 3 820 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 46 1/2 in Inside Width 15 3/4 in Number of Blades 10