Chibi's use an all-rubber sealing o-ring for both the top & bottom. The more expensive tanks I've used have Delrin/Aluminum/Plastic caps with rubber o-rings in a recessed groove. Honestly, The Chibi is definitely "rougher" (I believe Bill cuts the tubes manually) but the o-rings grip the carto throughout the length of the entire ring vs. just the thin o-rings the other ones use. Don't get me wrong, I have the DC 510 Carto Tank from MadVapes & it doesn't leak either, as I'm sure the MAP & other more expensive tanks don't, but I pocket the Chibi all the time & it is just as tough if not even more leak-resistant because the seals are so tight. I know I didn't do a great job explaining that, but if you have a MAP or other carto tank, slide the tank up and down the carto. You should be able to rather easily. With the Chibi, it takes a LOT of effort to slide it up and down.