52 In.H 40 In.W Non-Drnbl Alu Intake Louver Louver Type Stationary Blade Frame Type Flanged Frame Depth 4 in Mounting Style Surface Mount Outside Height 52 in Outside Width 40 in Rough Opening Height 48 in Rough Opening Width 36 in Louver Maximum Intake 5 600 cfm Maximum Exhaust 8 000 cfm Maximum Outside Width 52 in Minimum Outside Width 40 in Flange Width 2 in Free Area 6.6 sq ft Beginning Point of Water Penetration 766 fpm Maximum Air Velocity 3000 fpm Blade Angle 45 Degrees