I have a couple of charger power banks that are usually sitting at home when I need them the most. But using a wristband power charger is not only convenient to carry but also easy to charge because you won’t have to hold it or carry it inside your pocket. It charges any mobile device that uses USB including wireless speakers & Go Pros. Although it’s small & light but it provides up to 10 hours power depending on the device used. It’s one size fits all and is comfortable when wearing. It costs around 29$.