The LoKey 350mAh Key Box Battery is a discreet, transportable battery unit. The most apparent aspect of this battery is the fact that is it designed to look like a laser cut key component that is carried on a key chain. A single button releases the attachment port. That piece has a 510 thread attachment which is very common threading among industry tanks or cartridges. Both of which are not included in the package. It is able to output 3.7V of power.