AN / AND Fittings
AN / AND fittings have a 37° flare angle and use a class 3A/3B thread, which is a close tolerance, radiused root thread.
These fittings have traditionally been available in aluminum, carbon steel, stainless steel, and titanium. They commonly have fitments other than the flare, most commonly NPT, Base Seat Thread, or Hose Barb Type 2.
AN fittings are famous and desirable amongst auto enthusiasts for their classic blue anodized aluminum finish.
AN / AND fittings remain in prevalent use today, and they may alternatively be designated with an MS number, which are generally directly cross-referenced replacement fittings (functionally equivalent). For instance, an AN815 is equivalent to an MS24392. MS, however, is a very broad standard covering all kinds of hardware, and is not limited to AN fluid couplings.
The AN and MS designations for many fittings are being superseded with AS (Aerospace Standard).
In general, there appears to be a trend away from flared tubing in favor of compression type fittings, probably due to the fact that flares require greater special attention to craftsmanship (and more time) in assembly