CE4 coil style builds the exact same as a bottom coil. Only difference is instead of the coil being at the bottom of the tank and gravity helps feed it, instead its at the top of the tank and the wick feeds it by pulling the juice up to the coil. Same way an RDA works, wicks dip into the juice and feed up to the coil.Well, my Protank head is at the bottom, as are all the other ones I have. I thought CE4 was the skinny plastic tank. It's just the top-coil "style?"
I have three tanks exactly like that and the picture I posted was of one of them. They work surprisingly well and are inexpensive. If you can rebuild a bottom coil like the protanks coil, you can rebuild one of those.

