Thermostat Pipe O Ring

Hi all

I am going to change the thermostat ( not getting up to temp)

But I’ve discovered by looking at the thermostat a pipe must push in with a O ring on it

Doing a bit of research it appears to be 06B121687

Does anyone know if this is correct

I tried to call dealers yesterday but the parts department weren’t open

Car is

2 litre Tdi 170 manual

Cheers all