Attwood Louvered Marine Plastic Venturi Vent 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. Clean, contemporary, louver design. Corrosion-resistant ABS