Boat Vent III Boat Cover VentBoat Vent 3 is an improvement on Boat Vent II, which made its name in the marine industry over the last two decades through 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 over Boat Vent II: - 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.Please note: Boat Cover Vents are now assembled with the lower washer upside-down. This new assembly allows the vent to be pulled apart much quicker and easier than before. Continue to install the vents in the cover just like before. Refer to picture above.