AN stands for Army-Navy. The size specifications were established by the U.S. military during World War II and were originally used in the aerospace industry.

AN fittings use a 37-degree flare as the sealing surface. DO NOT use AN fittings with different flare-type fittings. This will cause leaks and damage to the fittings.

Each AN size refers to the outer diameter (O.D.) of the hose or tube that it’s used with. The numbers assigned equal the tubing O.D. in 1/16 inch increments. Each AN size also has its own standard thread size.

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Here is a list of torque values for each AN fitting size.

Note: 12 inch-pounds = 1 foot-pound

AN SizeAluminum FittingsStainless Steel Fittings
  • These torque values apply to AN connections only, not flared tube or compression fittings.
  • When using aluminum and steel fittings, use the torque for the aluminum fitting.
  • For best results, torque to the low end of the torque range. If it leaks, tighten it until the leak stops (without exceeding the max torque).
  • Lightly lubricate the threads and sealing surfaces with oil before assembly.
    • Avoid dry assembly whenever possible.

This AN fittings torque value chart was assembled by our friends in Summit Racing‘s tech department.