Once upon a time the "red" stoppers in the US were GAS rated, and the Chinese red stoppers were NOT.
However, many didn't pay real attention to that, made assumptions, had lots of tank stopper failures and decided to replace the RED Chinese stoppers with the US red stoppers, but didn't notice that the Chinese tank stopper necks were just a scosh bigger i.d., and then STOPPERS STARTED BLOWING OUT the front of the tank.

Sometimes, knowing the history can help one understand why we have what we have NOW.

My solution of choice has been, and will continue to be, to simply discard all Chinese fueling components, fuel lines, stoppers, etc. and replace with good ol' USA stuff that works. Worth considering, maybe, even if only to reduce the psychological workload of "What is going to fail?" that reduces our fun....