Boat Vent 3 is an improvement on Boat Vent II, adding value to covered boats by venting and tenting, preventing mildew and mold. Molded from the highest UV inhibited plastic on the planet, it can be installed to virtually any boat cover. Boat Vent 3 features four major improvements: 40% more venting overhanging top to allow in less moisture, 30 teeth on the washer for a better grip - Ergonomic reversible nut for easy installation.