The thread size for these fittings is Metric M5 x 0.8.
I got all my bits including a Flow control valve to dampen the gauges, from a pneumatics supply Co.
M5 x 4mm push in fitting, 4mm tubing into 4mm Push in FCV, and then into gauge.
You can use Imperial down to the M5,.
This M5 size is similar to "some" Imperial size because it's so small. the pitch doesn't intefere too much until the bigger sizes. Put a fibre or rubber washer behind it.
I think you all should change from imperial ....that way we all could say 10mm instead of 1 and 3/32nds/54 x 72 16ths........and 1/3"
