The eGo style battery was a first generation upgrade battery types for electronic cigarettes. Also called pen style, they vary in size in relation to the battery capacity that is built in. They are almost always rechargeable by way of a wall charger and adapter. Tanks, clearomizers, atomizers, and cartidges are screwed onto the battery threads. A push of a button fires the battery, heats the atomizer, and creates vapor! eGo Style batteries are simple to use, with set power levels, or variable voltage options for a more customized vape.