So far I am quite satisfied with the kayfun, I think it's a small step above the nautilus. Someone on YT said to stay away from Kayfun 4 (why, I don't know), so I got the EHPRO Kayfun Lite V2 Plus. I realize tho there is still room for improvement, eg. bigger juice channels. Now I am looking at a Russian 91 clone or a monster base for the Kayfun. My fear is that a Monster etc. might be too "airy"? TBH, the air flow of the Kayfun out of the box is perfect how I like it. I'd definitely NOT like something "airier", especially if I cannot adjust the airflow. (Then I could as well vape w/ my iSub)