Well this gets "sticky," as these fittings change some over the years.
ALL "standard" lines and fittings are known as 3/16 inverted flare. That is what they are called, and that is the callout for the flare nuts
However, various OTHER parts such as master cylinders and prop valves, etc, use NON standard nuts which were designed so they could not be connected wrongly. THAT is where the problems are "over the years." Some of these fittings are larger size (thread) flare nuts with 3/16 tube drilling through the nut, and some are proprietary thread.