This thermo-hydrometer is great for testing the fuel blends. Is it #1, #2 or the blend you ordered. Testing the specific gravity of a fuel can help in determining the blend you have. It has an API gravity range between 29 and 51 and works for all diesel fuels. The conversion table is built into the inner thermometer. Simply lower the hydrometer into the included hydrometer jar and see for yourself. Testing a diesel fuels specific gravity gives you the protection of knowing that the fuel blend is really what you ordered. It is inexpensive, easy to use and takes only a minute. Only 8" long it comes with the hydrometer cylinder and carrying case made of rugged PVC to protect this glass device. * Special order item. Item usually ships in seven business days.