Rocky, the hard line threads are metric but that particular thread interchanges with dash-3 AN almost perfectly (5/16-24 SAE thread; not the same as inverted-flair on hard line fittings). So a dash-3 AN fitting will screw in and seal, up to at least 1400 psi (my front brake line pressure), sometimes needing copper crush washers as the flair angles are at different depths in the metric fittings.
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