I've use the plastic Dennerle CO2 Check Valve they are good German made but they are expensive , Had them for a couple of years now so I end up wanting to try the brass ones I pick up on eBay for $4. ea x2 I paid $25. for the Dennerle CO2 Check Valve.I have never used a brass CV but on my riggs I have a CV close to the water and one before the regulator. It just makes me feel better.
Are the brass CV's worth the extra $? If they are I may just have to buy 4 and replace the plastic ones and the knock off ADA ruby CV with them.