A lot of people are not aware that many tanks can use coils from other tanks, and some coil brands are better than others depending on the wattage you vape and juice you are using, etc. Here is a comprehemsive list taken from Reddit of cross-compatibilty. Note we have not tried ALL these combinations so cannot guarantee their success. This list comes from DKB or DailyKnowledgeBomb on Reddit. Hat's off to him or her for putting this together for everyone!
How to use the list:
If your tank uses the coil in a category, you can usually use any other coil in that category.
i.e. SMOK Baby Beast uses TFV8 Baby coils, therefore it is compatible with any other coil in the "small" category.
Eleaf HW coils [Do not fit 22mm Vaporesso Cascade Baby]
E-XY T1 coils
Geekvape Aero Mesh coils
Geekvape iM1+4 coils
iJoy XS coils
Hellvape Hellbeast Mesh Coils
Jomo Tech Smartvape TC80 coils
Joyetech ProCore Aries coils [Do not fit 22mm Smok tanks]