These batteries are great. I use them mostly in flashlights/headlamps when I'm working on the car or just around the yard. They make my lights significantly more effective and my life easier. That being said, I do have an issue or two with some functionality aspects. 1. is when you pop the top off to charge it, the USB part you plug into doesn't fit snuggly enough on some USB ports causing it to fall out or not able to make a stable connection. 2. is the little cap has a tiny magnet so you can stick it on the negative side to keep everything together. Well it's not super strong so it is able to become lost easier. 3. They don't power everything requiring 3 AAA. I have no issue powering 2 AA devices, however 3 AAA headlamps don't work. This may be a an issue with just my lights or the batteries. Otherwise great power and convenient abilities.