I don't know what's going on, but it's going from bad to scary!! I have been using the 1.7 on an epower. There have been many inconsistencies, no quality control AT ALL. My tip is now too big and I have to jam it on, of course this leads to the tube co ing loose at the bottom because they are fragile anyway. Some are burnt right out of the box, more often lately. Some are way too tight of a 'pull' and some are way too loose. My friend was having trouble with her unit and batteries (I had given her one of these cartos). It appears that it fried both of her batteries. I was trying to figure out what the issue was, so I put the carto she was using onto my unit and it immediately became burnt and my led button glowed orange, ok THAT was scary!! What the fruit is going on?? It's not the vendor because I order from more than one. I WAS using the DCC's from smoktech, no real issues. I doubt that the switch from dual to single coil is the issue, more likely the time span and they are just becoming crap!! HELP!!