On the NA, what size is the transmission drain plug washer? 18mm?

 

...5 speed?

I think I got one laying on the garage floor at a friend's house. If I'm headed that way in the next couple days, I can measure it for you, since I'm pretty sure I drained it when I pulled it out. No promises though, life can be busy.

Honestly, you might be able to order the Mazda part (?) or just go to a auto parts or hardware store and find one that fits. I order a lot of stuff like that off mcmaster-carr when I know exactly what I want. I wish people would have told me about that website earlier in my life, it is great.

 

I don't remember what size it was exactly, but I bought this kit cause I knew I was going to need several and it worked out to be cheaper to get a box of various sizes. I want to say it's M20?