Sump drain plug size

Hi
Simple question: what size is the drain plug on a Mk2 3.8?. I need to do an oil change and want to replace the copper washer so just need the I/D of the washer.
Thanks

Hi Pud
I would use a 17mm i/d crush copper washer with a smear of hermatite or thread sealer for a 100% job
Cheers
Brian

Hi Pud That is assuming the hexagon head on the drain plug is 7/8 AF and it has not been replaced
in the past

Thank you Brian
Steve