Flaps are a great addition to any shroud that may have excess area where air can get trapped. The air inlet side of the radiator allows a specific volume of air, with flow, to enter the fin area. The same amount of air, and flow, must be able to escape the area immediately behind the radiator. Flaps provide a damper to ensure these two sides of the radiator are similar. The function of a flap is to push open at speed, when a fan is not in use, and allow air to flow out of the shroud freely. When the fan is needed, these flaps suck shut – sealing off the shroud, allowing the fan to pull air through the radiator evenly. DeWitts flaps are injection molded from a thermoplastic elastomer which provides a tight seal which aids the fan for increased air flow across the core. Flaps are easily mounted by drilling 1/8” holes for the tapered locking pins and square or circle exhaust holes behind the flap. This could be two 1.25” holes or a 1.75” x 1.25” square.