Oil pan drain plug size

[BERNIEHUMBER]

HI:
My problem(question) is trivial compared to some I have read.
I am off to change the oil in my S2 and when I do I want to replace the copper crush washer.
What is the oil drain bolt size?
I have a few washers in hand and I know the car is where getting a crush washer isn't possible..so go prepared.
Thanks