Its one of those little workshop tools that you dont think you need until you need it. It will tell you the condition of your battery as well as whether your vehicle is providing a charge to the battery. It will tell you if your battery needs replacing. I can post it free with any other purchase or $9.00 on its own. If you would like to buy some goods then click on your choices and complete your personal contact details and I will email you back with a price and payment details etc.