52 In.H 28 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 28 in Rough Opening Height 48 in Rough Opening Width 24 in Louver Maximum Intake 5 200 cfm Maximum Exhaust 6 000 cfm Maximum Outside Width 40 in Minimum Outside Width 28 in Flange Width 2 in Free Area 4.9 sq ft Beginning Point of Water Penetration 766 fpm Maximum Air Velocity 3000 fpm Blade Angle 45 Degrees