I bought all kinda of kayfun stuffs from
fasttech for my kayfuns. The things I bought worked just fine, the bellcaps were well spent money, used them more than the stock
tank. I also bought a few of the quartz
tanks and hmmm.....your putting a lot of faith in 2 thin orings holding the kayfun together and the tank partially blocked the fill port so it made refilling a nightmare. Too bad all my kayfuns seeped a bit from the fill port except my original Russian. Drilled the airflow bigger in a couple that improved them a bit, vaped my first .8 subohm build in a kayfun and again like my first cotton build in my protank, eyes rolled back and a sense of wow I can get use to this.... The kayfun filling became a hassle so I went looking for another tank and now its subtank mini's using the rba, they have performed amazing for us and not needing to upgrade in any way none too soon.