The tubing will be used with a lot of different things. I don't have a stealth adapter because to me it is silly but a lot of people like it. I can doohicky any stem to go in a cup so I never saw the purpose of the skinny top just to put a stripped straw on. I bought glass straws to drink with a while back to use to attach to my solo and INH and I like them so much I bring them with me on the rare occasion I go to a restaurant. I don't see the big deal of a glass straw sticking out of a cup. Take a look at the McDonalds cup on PV and see how they have it hooked up and decide from there if you need it.
EDIT: I didn't even buy the tubing which I believe was the second size that fits on the stealth adapter as it is useless to me for any of my setups. It is really small. I bought from 1/4" and up.
But the stem size is 1/2" which is the same size as the largest tubing so are they just for your other vapes?