Yes resistant to swelling and deterioration from oil, fuel, coolant, fire, etc, etc.
Please be wary of ANY product recommendations you see on these forums, folks. There is a reason auto manufactures don't use rubber to seal brake line fittings.
Oh, and what's the reason?
Because they have qualified engineers and not some internet clown making the decisions. BTW, they still use copper washers for this application, because they work and they do not deteriorate.
Go look up the 2018 Hellcat application. Copper sealing washers.
If you can't get them to seal quit buying cheap assed parts. Get factory washers if you can't find anything else because if they had the failure rate you have with them they would have quit using them decades ago. The problem isn't the design, it's you.
