Gasoline nozzles have safety and pollution control fearures. There are an automatic shut off design with the nozzle. The nozzle is able to stop automatically when the cars tank been oiled filled up so as to keep the filling place clean and the air not polluted. As gasoline flows through the nozzle, it passes through a venturi that creates a vacuum. As gasoline flows through the venturi, the air is being sucked in through a sensing hole. When the cars tank is full, the gasoline in the fill pipe rises and covers the sensing hole. The flow of air is effectively shut off and venturi sets off a chain reaction in the automatic shut-off portion of the nozzle. Product Specification Outer diameter:13/16" 15/16" (20mm 24mm) Connection Thread: NPT3/4" or BSPT3/4" Origin China