Guess it depends on what you're calling a
rda. You can get rebuildable CE4's, vivi novas, Kanger T2's, T3's, Protanks, etc, but they really aren't RBA's. The thing with RDA's is you make your own
coils at what ever resistance you want. I would suggest that you put the RDA's away for now, and wait until you fully understand how all this stuff works before you use them.
It would help if you gave us a link to what it is that you ordered. If you got Vision, Kanger, or iTaste heads you are probably OK, but if you got an igo,
kayfun, Phoenix, or gennie .... leave it alone for now.