This set of 10 adapters are designed to fit a 9v battery and convert it to a 2.5mm plug, making it a great addition to any Arduino project. The adapters are small and easy to use, and can be a lifesaver in situations where a specific power source is needed. They are made with high-quality materials and are built to last, ensuring that you get the most out of your investment. Whether you're a hobbyist or a professional, these adapters are sure to come in handy.