Never saw these before.

mopardude318 said

I have 3 of those plates, one on each of my small blocks. They seal right up, never leaked a drop. For the O-rings when needed, I called Canton and they sent them to me for free. I can’t complain. I’m happy to pay that price. I don’t know how to run a machine to make one…

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While on the subject kinda, of good O Rring items., billet thermostat housings with one are the bomb.
There is also a place that makes them from stainless steel with O Rings In Canada
I hate leaks. But good used steel is best! But if ya need shiney stuff O Ring Stainless is best and billet aluim second. Billet Specialties makes a good one.