The Gats Jar fuel testers are used to collect pre-flight inspection fuel samples. The jar then separates any co-mingled fuel and water by allowing the fuel to be poured back into the tank through a special built-in filter which traps the water behind. This allows the fuel samples to be returned to the aircraft instead of being discarded. This product is the only environmentally responsible fuel tester on the market. It also filters out particulate fuel contamination, and makes octane recognition simple and certain.This Gats Jar (EDMO# GATS/16) holds 16 ounces of fuel.