Coolant bottle cap

[John U]

I just finished flushing my cooling system and was looking through an old box of parts and came across a coolant bottle cap.
It is an RC 26 15lb cap. I think I got it from Special T years ago.
Anybody remember an issue using these replacement caps? I seem to recall they were frowned upon but I don’t remember why.
Thanks
John

[Ron]

I thought the RC-26 was 16 psi, which is 1 psi higher than stock (15 psi, AC RC-15).