Oil drain plug KZ650 - size of washer/o-ring?

Hello,

Can anyone tell me, as I don't have the possibility to unscrew and empty the oil atm, the size of the O-ring/washer on my 1980 KZ650 where I drain the oil?

Is it made of copper?

I use a M12 aluminum gasket from the auto parts store. They usually come in packages of 2 or 3.

The genuine Kawasaki washer is aluminum. Ed

Thank you!

Do you guys know the size? Is the M12 a 12mm or is the standard 10?

M12 = 12mm

The gasket ID is slightly larger than 12mm.

Partzilla is showing an oem price of 34 cents, so it might be cheaper to get a gasket at the Kaw dealer than the auto parts store. The Dorman pkg of 2 is about $2 at various places.