I just got mine today, from liberty flights. Its described as the Joye eGo 650mAh Pass-Through Battery Manual. I also just got my ego today, also, so the passthrough is all i've tried so far. It is MONDO convenient, though. I'm curious as to what the expected life of these things is personally, as i can't think of a reason to use a standard battery with this passthrough as an option, and dont wanna kill the poor thing with overuse!

Being brand new to the concept of a 'pass through' battery, i didn't realize it had a handy dandy cord that could be disconnected if i want to walk away from the computer for a while without switching whole battery. Handy!