The battery is clearly going to be plugged into an iPhone 6, so you can replace your battery with one that's better if your battery in your iPhone 6 has become bad or is completely broken.

The replacement doesn't take long, but you'll have to be a little sure of your hands to do it yourself, there are plenty of youtube videos that tell you how to do, and it's certainly not difficult if you just take it all from the end and follow each step exactly.

Has your iPhone 6 battery gone bad over time? Or maybe it's completely broken? does it go out when your iPhone 6 gets cold? All the parts can be fixed with a new battery, it is easy and much cheaper to do it yourself.

The battery is the same size as the one already in your iPhone 6, it delivers 3.82V or max 4.35V which is also normal. The size of the battery is measured at 3.7V usually done when measuring the size of this type of battery.