worth every penny! Most vehicle manufacturers drive the nut all the way in to save money. Then they put on a thin metal cap for decoration. These caps then swell and are almost impossible to remove from the factory supplied 21mm nut in a flat tyre. , or when you work with vehicles, you will feel pain. Use 21.5 to solve this annoying problem! works perfectly! I have used this product hundreds of times and have no problems! If a replacement is needed I will buy it again!