It takes the 18650 battery which gives the flash light more then enough power to last a long time. But what has happen to me in my job. It's that we would have a power shutdown lasting multiple hours. While we work in the dark. It comes also with a battery casing that allows you to put three triple A batteries. Awesome for when I am unable to recharge in the field.
The USB charging is also good. Since I do carry around a portable battery bank. I can charge the flashlight on my downtime.
Lastly I love the study metal construction. There has been many times when I drop things. And fear of damaging or destroying it. They way this is constructed it came take a beating and keep on working
I also forgot to mention it also has 5 modes which I like. Since I am use to headlights it is great to have them on the flashlight and SoS incase of emergencies.