I believe the Boge 510s come in 2.0 ohms and 3.0 ohms. At least, those are the ones i got from Liberty Flights. I prefer the 3.0 ohm myself but, I'd fully adjusted to taking long slow hits. The 2.0s were too hot and harsh for me. YMMV though. A lot of people love the 2.0s. I just add a few drops every 3 or 4 hours and keep it going. After 4 or 5 days, it's gets grungy tasting. I've read you can boil them to get rid of that. A lot of people toss them at that point. I'll give boiling a try when I have enough to bother.