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What's a -6 or -8 AN?

OK, so you're ready to order fittings for that new fuel system you just got. Now there's only one thing: What's a -6 or -8 AN fitting?

"AN" (Army Navy) Sizes were established by the aerospace industry. The measurements represent the O.D. (outside diameter) of rigid metal tubes. Basically, dash sizes are the numerators of fractions with a denominator of 16.

EXAMPLE:

-6 is equal to 6/16 in. which is equal to 3/8 in.
-8 is equal to 8/16 in. which is equal to 1/2 in.

In the examples above, a -6 AN fitting would work with a pipe that has a 3/8 in. O.D. A -8 AN fitting would be used with 1/2 in. O.D. pipe.

Here's a simple chart, just in case you don't want to do the math.

-02 AN is equal to 1/8 in.
-03 AN is equal to 3/16 in.
-04 AN is equal to 1/4 in.
-05 AN is equal to 5/16 in.
-06 AN is equal to 3/8 in.
-08 AN is equal to 1/2 in.
-10 AN is equal to 5/8 in.
-12 AN is equal to 3/4 in.
-14 AN is equal to 7/8 in.
-16 AN is equal to 1 in.
-20 AN is equal to 1 1/4 in.
-24 AN is equal to 1 1/2 in.
-32 AN is equal to 2 in.

The most commonly used fittings are adapters. These adapters connect an AN fitting to a pipe thread fitting. Most fuel pumps, regulators, and canister type fuel filters, come with pipe thread inlet/outlet ports. In order to use braided line, the ports need to be changed to a AN type of fitting. This is when a "pipe to AN adapter" is needed.

The most popular sizes used in fuel systems are the -6 and the -8 AN, although some high performance fuel pumps and regulators require a -10 AN fitting.

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