Attwood Venturi Vent White #231494F1Clean, contemporary, louver design. Corrosionresistant ABS plastic. For 3" or 4" I.D. ventilation system. Requires 1341 collector box for 3" system, or 1342 for 4" system. Install with #8 screws. Sized for installation even on highlycontoured decks. Attwood hullmounted vents are designed to install by fastening as a complete unit from either inside or outside the hull. Vent Size: 179/16"L x 23/4"H x 11/16"DHole Size: 2" H x 153/8" L