Something I thought I should mention. My friend bought 2 of the replaceable drunker coils and both had shorts and didn't work. I bought 3 of them but haven't tried them yet. Now I'm hesitant to if they just fail. The thought of going to all that trouble then to fill a tank and they don't work like hers makes me want to not use them. But at least we have the ceramic cups for parts they came with. Has any of you also experienced replaceable heads for these failing?