o-ring size for 12AX7 & AT7 dampers?

The max temp ratings I'd seen(way back when), for Viton and silicone O-rings, were 392 and 400 degrees Farenheit, respectively. Not far enough apart to make much diff, I thought. I've still got a package of the Vitons, from the original order, that I've never had to use, 'cause the ones in service stayed supple, and elastic. I've never actually used an IR thermometer, to see what kind of temp output tubes generate. I'll have to find now(all this has me curious).

Post back, or PM me, please.
I have looked at several sites and gotten various answers on temp tolerance of the various elastomers.
I don't even care what they will chemically 'put up with'. Some don't like gasoline or acetone or alcohol or whatever. That doesn't matter, either, to a hifi guy.
Since the silicone and/or Viton seem to be working, I'd skip Nitrile, Kalrez and Ethylene Propolene (EP) since they are simply not necessary.

Be careful to read the envelop temp, NOT the filament temp.

I got plenty.How many do you need? Email me .