Attwood Cowl Ventilator [1364A3]Cowl Ventilator Attwood hull mounted vents are designed to install by fastening as a complete unit from either inside or outside the hull. Ventilation hose (not included) twists into the bottom of the box to form a raised water barrier. Plastic vents are corrosion resistant, will not discolor. All collector boxes and vents are designed for intake or exhaust and meet ABYC H 2 cross sectional area requirements. For use with 3" I. D. wire supported