Keep rain out and let air circulate through the cabin with Beckson Marines Vent-O-Mate. Wind moving over the top of this vent creates a vacuum to automatically remove stale and damp air from your boat. A 5-knot breeze will exhaust air at a rate of 350 cubic feet an hour, helping to keep your boat fresh and mildew free. The Vent-O-Mate can easily circulate the air in 30 sailboat in about an hour and you dont have to worry about changing batteries or waiting for the sun to rise. Key Features Draft free Water tight Allows light to shine below No obstruction below deck Exhaust ventilator helps eliminate dampness, mildew and condensation Specifications Type: Passive Material: Plastic or Stainless Steel Warranty: One year Cutout Size: 4” Draw: Non-powered Capacity: 350 cu.ft./hr with 5-knot breeze