Reckoned to be stable and low less with (low and predictable) negative tempco but ISTR operating temperature often quoted as only 70 Celsius max, which might sound good but some valve kit could come close after a few hours. Also easily melted by soldering for too long or too close to the body (How do I know that
), I suspect that is why the leads tend to be very thin. This thin-ness means that they need careful handling when fitting and they can corrode through with long-term poor storage.
Worth hanging onto, not so prolific nowadays.