the original concept was devised by JohnYar Nikoo (JYNdustries LLC), who seems to have removed his videos. He initially used a european scuba tank as his sample cylinder, but it was single ended. The advantage to his approach was the ability to handle greater pressure, but it's still limited to the max. press. rating of the CO2 storage tank.
in my app, I decided to go with a swagelok whitey cylinder. the max press is the same as the storage tank, and it conveniently has two ends, 1/4" FNPT. the modularity is an obvious advantage.
some of you may know, but for those that don't, always use PTFE tape (wound three times around threading) with brass-brass/brass-stainless connections. hand tighten as much as possible, then mark across the coupling and tape with a permanent marker, then tighten 1 1/4 turns (for 1/4" NPT connections).