Door Louver, Material Steel, Finish Gray Primer, Louver Opening Height 16 1/2 in, Louver Opening Width 16 1/2 in, Rough Opening Height 16 1/2 in, Outside Height 18 1/8 in, Outside Width 18 1/4 in, Free Area 1 sq ft, Flange Width 1 1/4 in, Maximum Door Thickness 2 1/4 in, Minimum Door Thickness 1 3/8 in, Rough Opening Width 16 1/2 in, Blade Angle 45 Degrees , Adjustable Blades No, Intake or Exhaust Application Exhaust, Intake, Includes Fasteners, Number of Blades 30