With soooooooo many companies making "eGo's", 99% of them being knock offs, it's hard to tell. The only company who should be allowed to brand anything eGo is Joye... but Chinese laws are pretty lax.... with that said, it doesn't mean a knock off isn't good. If the battery says eGo-T on it, that means it should have a 5 click shut off feature.
eGo
batteries have 510
threading, so any atty that is labled 510 will work on this.
eGo's have an ouside
threading as well, this lets you put a heat shield on, or an eGo style atty, which goes over the outside threading. These also have 510 threading for the battery connection.
Now not to confuse, but there is also 306 atty's. If you drip, it's a must have, they rock. They also have 510 threading....
We are starting to see a trend now with brands naming their atty's now. For example SmokTech naming their 2.5 ml Carto's "Echo" then they tag on "E" meaning it only fits on an ego (which by default is 510 threading). "Echo-E"
Hope this demistifys the eGo for you.