If you are unfamiliar with valve cores, this is a MUST! You need this to check the tightness of your valve inserts from time to time, and now and then in the event of a flat tire - the tire must not be damaged, but the valve insert! This tool is easy to use and very reliable. I keep it with me along with extra valve cores when I ride! The right tool is very important. I'm so glad I have this tool from Park Tool! Richard