Attwood Louvered Ventilators are weatherproof and easy to install. The "state of the art" in louvered vent styling, these rugged, ABS plastic vents are easily installed on today's highly contoured deck designs and have an adequate opening for 3" or 4" ventilation systems. Made from ABS plastic, these ventilators are durable and will not rust, discolor or streak. Louvered vents are built to keep unwanted elements out while allowing air to pass through. These vents are designed to be installed as a complete unit from inside or outside of the hull. Attwood drilled these vents with four holes for #8 screws; they contain no sharp edges and are backed by a one year warranty. Specifications Type: Louvered Material: ABS plastic Warranty: One year Cutout Size: Surface Mount