3.7v 1200 mAh Lipo Battery
Small, light weight power source for wearables and other portable projects.
You can't beat the power density of LiPo batteries. They seem down-right miraculous when compared to alternatives technologies.
With great power comes great responsibility so make sure that you buy these with caution. There are a lot of cheap batteries that look the same but don't have internal circuitry. This is a case where reviews are key!