The X1 / TX1 coils feature a 0.15 Ohm resistance and utilise a single Kanthal mesh coil build. These coils should be used between 40 - 90W.

The X2 / TX2 uses dual Kanthal mesh builds and registers a 0.2 Ohm resistance. These coils should be used between 40 - 80W.

The X3 / TX3 has three Kanthal mesh coil builds and features a 0.15 Ohm resistance. These coils should be used between 50 - 90W.