Always, I am not sure if there is a truly leak proof tank. The Rogue clone I got for the bottom fed mod is mostly leak proof. But the taste was simply not there for me. The Quasar was bought used, and it is an authentic. It has been reliable, and pretty leak proof too. But the top cap is very hard to pull off, and put back on. (even if you wet the o rings) That is not a problem because you don't need to take that top cap off very often. The Derringer has been very good for me, and only leaks if I over fill it. I have found if leaking is a problem, bottom fed atty's are better. If you keep the mod upright, no juice will get out. Just take a puff or two, before you have to put it up. With no juice in the well, it won't leak. Now if you leave it in a hot car, it might leak possibly. I bought the reducer tube for my Reo. It is supposed to help with very hot climates. Also cut a v in the bottom of the tube, it will help too. As far as tanks, I think all tanks can leak, under the right conditions. I am sure someone will be along to correct me soon.