Robbot (spelling form China?) Tech was the only manufacturer on one of them. They have 5 K4's on their site.......hmmm.......
I bought Tobeco's Kayfun (not the LT), and it had issues: threads, leaks, kind of a hassle. Ended up getting 12 Kayfuns/ K LTs of various prices plus a few Russians from Focal and a few other tanks that are stashed somewhere. The old "vapapocalypse",

lol! Still have a bunch of 100% nic in my freezer and 2 gallons of VG/PG, with the various flavorings from the usual suspects.
Bursardo has sold me again on something! NOT the ProV 3 though, I have the full size 2.5, and it's still working like a champ. I can do 1.0 builds on it (occasionally I skip a loop and end up with a .9, no problem, still fires), which is good enough for me.
So if any of you want to mosey over to Focal and give me suggestions, here's the link to K4's:
search Result:Kayfun V 4 in focalecig or this for all colors:
search Result:Kayfun V 4 in focalecig
Don't know if the links will work.........they didn't way back!