Button Top 3.7V 5000mAh(21*75 not 18*65) Lithium-ion Rechargeable Battery Type-C Input/Output Protection Circuit Built-In Large Capacity 3.6V Replacement Battery for Flashlight, Headlamps etc 2 Pack

1. Sized as advertised2. Works in devices speced for 21700 buton top batteries3. Charges with USB C standalone or in devices with onboard charging.This is a BUTON TOP 21700 battery. Not a flat top. Most negatively reviews are based on allegedly incorrect dimensions. Most people don't insist that these rechargeable 21700 batteries are all custom made with a range of sizes depends on the specs. Many protected cells with USB C charging built-in will be up to 750mm in length while some flat tops will be substantially less than 700. And then you have variences in device battery bays that will only work with shorter, standard or longer batteries. This on works for devices made for protected USB C chargeable cells.The fit in my Coast headlamp, Fenix PD36R PRO, and Diverite dive torches. The charge while instaled works on all three devices and the batteries are charging with my fast charging block.These batteries fill my need for travel friendly high capacity batteries for my EDC and specialty lighting devices. I will amend my review if perfect is bad over time.

I just received my batteries. I charged them, and put one in my Nightcore M12S and ran it on the highest setting (1800 lumens) until it dropped to a lower light. The battery lasted for 2.5hours. That’s longer than the original ever did.

Mine overheated when charged, and it was an operation at the same time as it was charging be careful with this one guys batteries nowadays are kind of dangerous

PERFECT FIT/SIZE (( BUTTON- TOP BATTERY !!!! ) 21700 type 3 5000 MaH true power rating. YOU GET WHAT YOU PAY FOR ! Awesome batterys perfect length width EVERYTHING! Usb C charging/ ex Power Port flashing blue light when its charging Fits my led work light Perfectly! Also chargers inside my flashlight ! Everybody’s return this because its a Button Top ! People dnt pay attention anymore ! One review talks about overheating Every lithium ion battery gets warm when charging FYI My $1400 Iphone gets warm when charging Nature of the Beast I can also charge my IPhone w these also Plus you use a good high wattage charger Also helps w battery getting warm Cheap chargers cause warmer temps Took a chance these would work because the Other Reviews we Not Much Help so i did this review to Clear the Air . They even come in a nice carry case! Worth every penny By the way that magnetic work light in pics is the best light on amazon also! Good luck slow up Pay Attention. THE LISTING PICTURE SHOWS A 2175 Battery I still revived a 21700 like i wanted so probably help if they fixed the picture and put the picture of the 21700 battery like in my pics!

I used this product for a custom application, so I won't comment on the form-factor. It was perfect for my needs, and I had some flexibility with regard to the length. I measured the energy capacity of this battery, starting with a full charge, and draining the battery at 1-amp. According to my measurement, this battery delivered 4749mAh (16.457Wh.) It replaced a NiMH battery of the same physical size, but the NiMH battery only provided 2000mAh when new. Since the new battery has built-in USB-C charging, I don't need to carry around the NiMH charger that originally came with the product.Under different test conditions, I have no doubt that this battery may be able to deliver 5000mAh, and 4749mAh is close enough for me. Many batteries I've tested don't even deliver half of what is written on the label...

Good to have as a backup

A good battery I am sure. Be warned it WILL NOT Work in an Plight Flashlight. Same number different design.

I have 2 stars because the USB-C functionality is nice, but after fully charging the pair of batteries I found that they didn't fit properly in several of my devices, and the one that it DID fit in, it wouldn't power on. Live and learn, I guess.