I own a variable voltage box mod. It has worked great for me. It has a 510 connection. I have been using regular cartomizers for a while and have had no problems. I just got a new vz rebuildable bottom coil tank at 2.5 ohm. It worked great for about 5 mins and then it quit working. If I pulled the battery and put it back in, it would work for one puff and then quit working again. I can keep pulling the battery and putting it back in and get one puff but it won't just work like my regular cartomizer. So I hooked up my old cartomizer and everything was fine so I don't think that it is my batteries. I tried turning the voltage down but nothing worked but with my old cartomizer it worked fine at any voltage and my regular cartomizers are 2.5 ohms. If someone could tell me what I am doing wrong, or what the problem could be, that would be great. I use protected trustfire blue batteries. It only happens with this clearomizer.