I don't know what it is, but my CLS at the end of this 50 ml bottle is just tasting.... off. It's not as decadent as it once was, maybe i'm just so used to vaping custards and they all are getting a bit muddled but I am truly bummed. I been using on my dripper at about 20 watts and the kayfun anywhere from 9-14. So nothing different then I did. Makes me a sad panda, I want my CLS to "pop" again.