Manufacturer LazBlinds. Blinds width will 1/5″ narrower for a snug internal installation. For Example, if your windows are 30″ wide, order 30″ or slightly less for internal installation. For Example, if your windows width is 30″, order size 34″ would be okay for outside mount.,⭐(Pls Note) Fabric width is 1 4/5″ narrower than the shades.