The 510 tank is pretty small. Holds 0.5-0.8ml of
juice, and looks like a DT on a 510-T atty. The eGo-T Type A and B are other choices for your eGo. The Type B's hold more juice, but don't look too big on the eGo's.
The 510 tanks have a round mouthpiece, and the eGo tanks have whistle tips.
Hope that helps.
edit: Of course there's also the 3ml Liquinator if you wanted a carto tank, but you would need a washer or something else to stop it from sliding down on your eGo.