FloMAX Fuel Vents are manufactured using 100% metal components. A billet aircraft grade anodized aluminum cap provides superior impact strength as opposed to the less expensive and weaker plastic and cast aluminum caps on other vents. The float and sealing balls are housed in a ridged ball tube, not the flexible and easily damaged ball spring. This will ensure a positive seal that will not be damaged by vibration and movement. FloMAX vents are available in all standard configurations including male or female threaded outlets, anti-vandalism sleeve, and half couplings. Stem tubes are available in standard 5", 7", 9" and 12" lengths as well as custom lengths. To determine proper vent stem length, the ullage, or air space remaining in the tank should be 12-15%; the length will also depend on the tank shape - ie. a curved top tank requires a longer vent. Note: Anti-vandalism sleeve actually works as a tank bushing, reducing an open 4" Male NPT tank port down to 2" Female NPT, and can be aligned to add a padlock.