The Beckson Vent-O-Mate Ventilator is powered by a slight breeze and will automatically exhaust up to 350 cu. ft. of stale, hot or damp air from inside a closed boat eliminating mildew and odors. Low profile. 2-1/2" H. Reduces deck clutter. Ideal for heads, galleys and the forepeak the vent will prevent damage to interior wood cabinet work due to moisture. Easily installed, the vent requires a 4" diameter hole. Rain cannot enter even when open. Comes with an 8" protective cover.