All kr8 stuff should be at 3.7V. The problem I found with the PigCig is that though it's kr8-threaded and 3.7V, it doesn't actually accept regular kr8 cartos like from V4L or others. The difference is in how the battery and carto connect. On a regular kr8, for example from V4L, the carto has a groove cut in the end and the battery end is flat with a hole. On the PigCig, the battery end has that groove cut in it and the cartos (I picked up some of LeCig's mega cartos) are flat. If you try to put one of those cartos on a kr8 or one of the kr8 cartos on the PigCig, you get no airflow and thus no
vape. I contacted LeCig about this and Mike said that he's looking into the possibility of an adapter but for now the two are not compatible.
I don't know if the Elegant Easy or other kr8 fat batts have the same limitation, but it's very important to find out before ordering. I got the PigCig because I have a bunch of other kr8 stuff, but as it stands now I can't actually share cartos. I still use it, but it would be much more useful if I could swap a carto between my kr8 PT and the PigCig rather than having to carry both types.
Edit: Looking at the large image of the Eden starter kit xg4bx linked, the battery connection looks exactly the same as on the PigCig. And I need to amend my statement above -- regular kr8 cartos on the PigCig and similar get too much airflow and apparently no battery connection. They just don't vape. PigCig cartos on a kr8 battery get 0 airflow and thus can't vape.