By integrating air filtration into the conventional pressurized fueling vent, the V150F features an airflow check valve to protect your fuel tank from contaminants. Outbound air and fuel vapors are guided away via a one-way check valve, while incoming air undergoes filtration through a 3-micron filter. Similar to other vents, the standard level control stem is 5 feet but can be customized to 7 inches or 12 inches.