Nitrogen type for PCP fill?

Nah, it's actual grade here, not pressure. The scientific community and other communities depends on the quality. UHP isn't needed for airguns. From Praxair, note the significant digits. IE: 99% is not the same as 99.999% -- https://en.wikipedia.org/wiki/Nine_(purity).

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Yes and the next page shows that the only 6000 (6K) is the ultra high grade. Unless I'm missing something. Not much point in buying a 4500 psi tank is there?

Yep, those are my thoughts. I went with a very large 6000psi vessel. Now a couple weeks ago I bought a YH to use as a booster to top off my smaller tanks using the nitrogen tank once it falls below 4000psi. I bought a Palmer Paintball in-line stabilizer so that I won’t have to adjust my regulator all the way down to 30 psi to run the YH. The regulator should be in this week and I’ll post a pick once it’s up and running.