Smok TFV12 Coils.
These coils are £5 each and there are 3 different options to choose from.
 
Q4 Coils
0.15Ω Quadruple Coils
Brings smooth taste
60-190W / BEST: 90-160W
 
X4 Coils
0.15Ω Quadruple Coils
Brings deep and rich cloud taste
60-220W / BEST: 100-170W
 
T12 Coils
0.12Ω Duodenary Coils
Cloud vapor chasing
60-350W / BEST: 130-200W