Use with plastic louvered vent, with two 3" I.D. wire supported ventilation hoses. Box fastens to vent with screws or pop rivets, vent then fastens to the deck. Corrosion-resistant plastic. Cut-outs for two 3' I.D. hoses. Corrosion-resistant plastic. For use w/plastic venturi, flush louvered, or trimline vent.