MSW’s Take: we love using NACA ducts on the rear windows of our race cars. They provide a great deal of air flow, even without the use of a blower fans. Absolutely indispensable for driving in the hot South.
For use with 3″ ducting hose. Made of molded plastic.
Outside flange dimensions (can be trimmed): 6″x10.75″, 4″ height.