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Here is a short guide to AN and NPT thread types for stainless steel hose fittings.

AN stands for Army-Navy, and is the military standard for measuring hose and fittings. It designates the outside diameter (OD) of the ridged metal tube that is compatible with each size of fitting. Still today, this AN dash standard is the benchmark for military, industrial, and performance hose applications. These dash sizes are expressed as the numerator of the fraction, with the denominator always being 16. For example, a –04 port is 4/16 or ¼-inch.

NPT stands for National Pipe Thread, and is the standard for metal pipe threads in the United States. Pipe and fitting sizes are measured by their diameter, and are expressed in inches, such ¼-inch size.

To use stainless steel hose on the MR2, you will have to use AN to NPT thread adapters. Be warned that in some applications a metric to standard adapter will also be required. The pain, the pain…

* Courtesy of Aeroquip.