External Co2 diffusor - how to connect Co2

[Rudi]

How do I connect the CO2 pressure hose to the external diffuser?

When I try to unscrew the "union nut," I only ever get to the spring inside. I suspect that the part I'm unscrewing is actually made of two pieces, but the outer thread is too tight, so I'm always unscrewing both. Or is the CO2 pressure hose simply forced in?

Thanks Rudi

 

[Rudi]

Here a picture

 

[Administrator]

Press the surface, then use other hand to unscrew it.