The 12oz. Gats Jar fuel testers are used to gather, pre flight inspection, fuel samples. It then separates any co-mingled fuel and water, by allowing only the fuel to be poured back into the tank through our special built-in filter which traps the water in the back of. This permits the fuel samples to be returned to the aircraft as an alternative of being thrown at the ground. After the water is trapped within the container, and the fuel is back within the tank, the captured water can then be thrown at the ground without polluting the soil, and the ground water with leaded fuel.Studies indicate that over 3 million gallons of AVGAS gets poured at the ground on this country annually just by sampling fuel throughout pre flight inspections. This product is the one “environmentally responsible” fuel testeron the market. It also filters out particulate fuel contamination, and makes octane recognition simple and certain.