The cartos I swear by are Bloogs (yes, 808's), and I have tried many. They are a horizontal coil, hold a ml, and last forever. I top off about 2/3 of the way through and they are beyond easy to fill. They are 2.6-2.8 ohm (as Bloogs run 3.7-4.2v) and are great on my backup Ego too, but the Ego...