3.7V 3800mAh Rechargeable Lithium Batteries with Micro-USB Cable - High Capacity 30A Button Top Batteries for Flashlights, Headlamps, Doorbells, RC Cars, Toys & Electronics (4 Pack) - Perfect for Outdoor Camping, Emergency Power & Home Security Devices

Not much to say here. They do the job. Their output is decent and they hold a charge well too. Very easy to recharge. Only have it 4 stars because it should hold its charge longer while not in use. IMO…..Love these for their built-in charging capability. Just disappointed that there is no on-board way to check the state of charge. As soon as someone wants to make the battery also the charger, it seems it's incumbent upon them to provide everything the charger does too. This offers no way to know when fully chaged.I like the fact that I don’t have to have a separate charger for this. It’s easy to plug in and charge and holds it for quite a while depending on what you’re using it for. I didn’t have any issues at all with this and not having to carry around a separate charger is awesome.We have several flashlights that I wanted these batteries to work on. They charge good but the button top on this battery set is more of a flat top, so on a few of out flashlights they do not make contact. Other than that, they are a good battery set.Please note the size of the batteries for compatibility with your equipment. I ordered this set of rechargeable batteries for my husband to have as a back up when we run out of the more powerful battery packs that we have. So far he tested it on a flashlight and a headlamp that he takes when we go camping and they have worked really well. They do not lose charge fast and we haven’t had to recharge them so far.Please don't have a size on them so I thought they were going to be a standard like double a or triple a and they are not they are longer than that so I don't really have much use for them now but I love how easy they are to chargeI bought these batteries as backups for my hunting flashlights. They are a perfect fit and have held their charge as expected. I plan on purchasing another set before the season hits.I honestly ordered the wrong battery so I'm not able to say that these work. What I will say is that they are nicely packaged, the charger itself is very nicely made and seems like it would work well with the right kind of use.