I do not know what Smoke Free uses. If Smoke Free is about 9.2 diameter and the battery has inset (female) threads and the cartomizer has the external (male) threads, then it may be RN4081. To check, if you can find a 7-11 with
njoy 2-n-1 or Njoy Npro cartomizers, buy some and try them. That Npro model is RN4081
And most standard cartomizers of 9mm+ diameter ecigs hold about 1 ml
And warning - you probably have auto
batteries (no button) and auto
batteries can be killed by leaks from cartos because autos are dependent on a drag sensor through a hole in the threaded end of the battery. SO never fill on the battery and always make sure the carto is not going to drip before putting it on your battery. if you determine you have RN4081 then consider picking up a manual RN4081 battery from AZSmokeFree.com (the manuals are totally sealed on the end)