They work great with a USB charger that has two ports, one of which supports fast charging. Everything worked as expected. However, the openings for the USB port are too small. It's such a simple thing, but it literally takes a lot of effort to get the USB connector into the plastic casing that surrounds each port. It might get better with use, but in my many years of working in IT, I've never had a USB cable that didn't easily plug into a port like this. They charge devices perfectly (Samsung Galaxy Note 9 and S8+, Kindle Fire, multiple iPads), which is their main function, so that's good. As an electrical engineer I can say they are probably not as reliable as the ones that came with my phones. They don't appear to have inrush current limiters as they can produce a small spark when plugged into an outlet as others have noted (this really isn't a huge issue but something to watch out for). A USB case that is too small is a bit annoying. but I don't unplug/plug that end very often. Your mileage may vary. I was debating whether or not to deduct more than one star, but given their price and the fact that they perform their intended function perfectly, I only deducted 1 star.
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