A valve core is a small one-way part that lets air enter a tire and stops air from leaking out. Common types include American (Schrader), French (Presta), German, and British valve core, with the American type being the most widely used. Most valve cores are made of copper and have several parts that work together to give strong sealing performance. Besides tire use, valve cores are also applied in many other fields, such as nitrogen gas springs, accumulators, gas valves, fire extinguishers, and life jackets.