@jkaniarz forgot i had a photo, my 'keg coupler' is a bit cheaper-looking than the one I linked (was in japan at the time, and couldn't find all of the exact same parts hehe)
So yea, I'm re-using the same regulator with the paintball tank, so the adapter is to couple those together.
@rek Check out the tiny regulators on this setup. They’re even smaller than what I had. https://hackaday.com/2013/10/16/going-mobile-with-your-air-tools/