Heng's Exhaust System. This unit consists of an attractive exterior vent cover designed to keep rain and dust out of your vehicle with an outside manual release damper. Once the outside manual release damper is unsecured, the damper automatically opens when the range hood fan is activated to allow cooking odors and smoke to be exhausted. The damper automatically closes to prevent insects and dust from entering when the range hood is not in operation. The manual release damper must be secured before traveling. Dim.: 4.62" x10.88" . Cutout: 4" x 10.86" . Bright White.