Thanks Rob, I used the red o-ring ones in my Melo 3 mini and it was okay, i've been using the Target Pro tank I got from you and it's been awesome. I just saw now i've got the 0.6 black o-ring in the box will give it a go. But this tank has performed well, only thing I don't like is screwing the top cap off to refill, got a blister from trying so hard the other day but I prefer it to my Melo 3 mini.@Chad B these are the best of all but I think these were just a batch that Vaporesso made when they ran out of the hex stock (and I'm guessing) and these are as scarce as hens teeth... the 0.6Ω with red o-rings are second best.