Drain Plug size for manual gearbox? M18 or M20

[Click_It]

Hey guys,
My 5-speed manual’s been leaking gearbox oil for a while now — probably the washer, but I want to replace the plug too. I’ve always reused the original one.

Does anyone know for sure if the plug size is?

M18 x 1.5
M20 x 1.5

If in doubt, I can just buy both, it's going to be one of them. Interestingly, my huge workshop manual doesn't specify this either.

Cheers!

[Click_It]

Update:

I found an older thread saying the part could be the "Doorman 090-075 bolt" which is a M14 x 1.5 part which makes sense as that matches the sump plug so it's going to be M14. Dunno why I was thinking the other sizes.

[Click_It]

If anyone needs this one day, it is the M14 x 1.5 part but the aftermarket magnetic tip plug/bolt I bought didn't fit. It did, but it felt like it was ripping into the thread and it was also 10mm longer than the stock part so assuming it wasn't too long, I don't think going back to the stock would would be possible afterwards. So in short, i didn't use it and just replaced the copper washer. So far leak free.