Guess some would say the replaceable coil heads can be rebuilt though I have not been happy with the effort or results when going that route. I have a 30mm Aerotank Giant which has plenty of room and a couple EVOD glass which are considerably smaller in diameter. Both use the same replaceable coils. I would rather use a single 1.5-2 ohm self-wrapped coil on a deck made for rebuilding. My understanding is some manufactures offer this option. Perhaps there is an aftermarket solution?