ego atomizers. 2 or 3 drops is enough. Do not over fill them. Do not try to burn them empty. There are examples on how to clean them on U tube. After 6 months I have found it don't matter how well you take care of them they will eventually burn out and have to be replaced. By far my biggest disappointment with ego is the life span of the atomizers. I was smoking cheap illegal garbage sticks made by the native Canadian indians. the cost is very low which has me spending more on electronic cigarettes but you get what you pay for. They were killing me and I could feel it. It's worth the extra costs to replace atomizers just for the health reasons alone.