The problem I had with the Kanger RBA was that it had a .5 coil that was 2.5 mm inside diameter. I prefer a 3 mm id, it allows a little more room for the cotton. But if you are not into winding your own coils then you are stuck with the smaller coils. I get my RBA supplies from Lightning Vapes, They don't sell tanks they specialize in RBA supplies. They have cotton bacon and anything else related to rebuilding coils.