That Ista bubble counter is the one most commonly used. However, they should be swapped out every year IMO as I don’t trust the quality of it’s internal check valve. I’m not a fan of those and would rather use the bubble counter on my CaRx. Having that bubble counter fluid fluid that close to my expensive needle valve makes me nervous. Intead, I rely on the CaRx bubble counter and attach one of these, more reliable CO2 check valves inline.
https://www.marinedepot.com/Dennerle...COCACV-vi.html