I bought that same Aliexpress fill adapter and almost had a catastrophe. While I was filling my SCBA from the Yong Heng compressor, I heard a pop while I was in the room adjacent to my shop. I went in to my shop to see what had happened and found that the gauge had exploded and there were shards of glass and glycerin everywhere. Fortunately I wasn't in the same room when it happened. I have since replaced the gauge with a larger diameter/higher quality unit and all is well. I always wear safety glasses when working around HPA equipment for this very reason. The gauge failed around 3000 psi.
Brian,Why liquid filled? It's really of no use in this application and certainly not needed.All the glycerine does, is dampen the needle from pulsation and vibration. Neither is present when moving air from a tank to gun.
My question is how accurate is the gauge??? If I'm filling my $1000+ gun - I don't want to overfill it. And on the other hand if I'm filling my gun to the "Sweet spot" - is it that accurate?? My friend bought one of these fill stations and we went to check the accuracy of the gauge - we attached it to a full tank and had the end plugged and the gauge went to 3000 psi and stopped - this was a full 4500 psi tank. We tapped on the gauge and the needle moved to 4800 psi. I personally don't trust all this stuff coming from china that isn't built to specs. Its just a matter of time before someone really gets hurt by this stuff - I hope that I am wrong!!!