Hey guys I recently purchased my first rebuildable, the Cheetah 2 RDA. After a lot of fiddling about I finally managed the wick the thing properly lol anyways I'm wondering what's the best way to go about getting replacement O rings. I especially need them for the top caps base as when removing the cap to fill it puts pressure on the ring. What should I do buy a mixed bag and hope that one fits or..? Any help is appreciated as always, thanks guys