It's just a slightly beefed up 510. The standard uses 180mah batt's, the Mega has 280mah. A standard eGo is 650mah and the Riva is 750mah. They're all good units so if you don't need the fat batt, but want something with a bit more power than the standard, the Mega fits right in there. It should give you around an extra hour of runtime over the standard.