"Nicro Ventilation Air 500 . Nicro engineers have created a passive wind-powered vent that moves 600 1000cu.ft./hr. of air with just a 15-knot breeze! A locking shut-off damper may be operated from below. Passive wind-powered Durable white plastic housing Screws directly to the deck Uses standard 3"" hole Allows the use of Nicro trim ring...