[V8] O-ring help

[Ingo Rautenberg]

So I'm replacing the O-rings that are mounted to the coolant lines  
that go to the back of the head on the 4.2, removing the blue rtv  
that had been used to (ineffectively) cure a coolant leak from the  
previous owner.  Well, now I need to replace the O-rings and I have a  
bunch of metric ones, but only have the Audi Part number:  077 121  
437A.   Anyone know the size of those O-rings?

TIA

Ingo