The words “NACA Duct” usually go by so fast that they sound like “Nackaduck”, but a NACA duct is really just a specialized type of duct. Ducts are hoses or other devices used to move air from one place to another. brings air into (in our case) a racecar in a very special way. Clear NACA ducts can be seen in the rear windows of NASCAR cars – there are usually two or three in the window. Carbon-fiber NACA ducts sit in the front of the car.