Sea-Dog Gas Tank Vent - Die Cast Zinc Chrom PlatedGas Tank Vent Die Cast Zinc Chrom Plated These gas Tank Vents provide the needed air flow to maintain proper fuel flow while filling and during use. Vents compensate for changes in tank level due to consumption, as well as temperature related expansion and contraction. Designed to prevent vacuum build up during use, which can disrupt fuel delivery, they also double as a pressure release valve for the gas tank. Helps prevent fuel spills, blow back, and