Our vents and fill caps are specially designed to hold a constant tank pressure, reducing evaporation loss, contamination intake, over expansion, and contraction of the tank and are safety fittings on vent lines. These caps are generally used for above and below ground storage and tanks holding gasoline or diesel. Additional elements can be mounted on top of the filler cap for specific operational purposes. The construction meets the safety requirements of PESO and Chief Controller of Explosives. Vent Caps are usually 2 and 3 sizes. Standard Dip Caps are 2 size and are used for dip tape or dip rod measurements.