Another vote here for the 808 and the Kanger horizontal cartos. I have a couple of Ego batteries and still long to add an 808 kit to my arsenal but can't justify it until at least one of these Ego's bites the dust.
I got a 510 battery to 808 carto adapter that I use on my eGo
and I got
"The Best of Both!"
($4.50 for the adapter!)
and I got
"The Best of Both!"
($4.50 for the adapter!)