I was just wondering why the makers of the kr808 haven't jumped on the boat as far as a factory produced big battery , Iv'e seen the ego , and i have a riva, these are both above 650 mah the riva is 750 mah . and I can tell you since i have got this it is all I use , i use both 510 & 808 cartomizers , i just have to use an adapter .I get about 8 hours out of one battery and it's not really that much bigger , just a little longer than a regular 808 battery but it's bigger around , but it actually looks good. I'm just hopeful ( healthy competition is a good thing )