We get asked this question quite a bit from enthusiasts that are new to AN fittings, so here’s a quick explanation:
The AN specification is a particular type of fitting used to connect hoses and/or rigid tubing that carries fluid. It was originally developed for the US military and dates back to World War II from a standard agreed upon by the Army and Navy, hence AN.
AN sizes range from -2 to -32, although larger sizes can be made if desired. This sizing system is called a “dash size”, and is measured in 1/16-inch increments. For example, a -8 fitting would be 8/16-inch or 1/2-inch. It is common to incorrectly say “minus eight” as the hypen looks like a minus sign, the correct term would be “dash eight” or “dash ten” depending on the size.
AN fittings use a flare to seal the connection. There is a 37-degree machined flare on both the male and female sides of the connection that forms a metal-to-metal seal. There are other standards that use a similar system, such as JIC and SAE flared fittings, but these may not be compatible. Mixing them can cause damage to the fitting or a leak at the flare.