So I searched google and found this thread on the 3rd gen section
https://www.rx7club.com/3rd-generati...asket-1061723/

The only reason I'm feeling cheap is because the factory one is a $20 o ring. And last time I ordered from mazdatrix I didn't ask how much shipping was, and it ended up being close to $20 for a $30 order on oil filters and a brake line. I do need some stuff from McMaster anyways also. hmmm, maybe ill break my old o ring and measure it

 

I have packs of both sizes for FC and FD from MMC. I haven't compared them to stock to verify for myself, but plenty of others have.

 

i guessed at 102mm(the one i tried to measure was quick triangly, i found nothing thru local venders. i did find some orings on ebay from china for really cheap

 

Do you know what size was for the fc?