There so many variables. What type of RBA or RTA. On a dripper I usually do a dual coil, 24 gauge kanthal 5-6 wraps (sleeper coil) on a 3/32 drill bit, it will get you in the .3-.4 ohm range. On an RTA (Kayfun, Aqua) I use 26 gauge kanthal, 10 wraps on a 3/32 bit. Hits right at 1.2 ohms. I have done a lot of differing builds, but the above two are my favorites. If you are looking for a great dripper, I think the Paradigm Magma is great. The build lines up perfect fully with the holes. I really love VLS's Vulcan RDA, great price for a dipper. Hope this helps.