I love my Kanger T3Ss. They hold just the right amount of juice, the bottom coils are rebuildable and interchangeable, they're 510 threaded. I've tried other systems, but always come back to the T3s because honestly, I like the act of puffing!! The downfall of the T3S is that they are made of polycarb. And I don't know how often to change them out due to their material. Any suggestions? And I'd sure like to find a good resource for buying them.