Hi Argus,

Your logic in detailing the originating source of the flared connections appears to be spot on. That would have been my guess. When the "*****s" were being developed, Frigidaire was owned by General Motors.

I think it's also interesting to note that two types of flare nuts were made (long shank and short shank). The long shank version provided more support for the tubing at the flare, than the short shank versions which seem to be so popular here in the US.

What is the common type everyone uses?

In my later service years I made the switch to using hydraulic fittings and tubing, instead of flares and copper tubing. This resulted in complete reduction of problem leaks and call backs due to flared connection issues.