I know for a long time I wrestled with the question of how AN fittings are sized. For those that have also wondered, here's the explanation:

The AN# (ex - 4-AN) is the numerator in the equation X/16, where X = 4 for 4-AN. This gives you the nominal ID of the hose that comes in this size. The nominal ID for 4-AN hose is thus 1/4 inch. You can be assured that a 4-AN hose will fit snugly over a 1/4" OD hard line.

The AN system was originally designed to give the OD of hard tubing, so this is what the nominal dimension is for - the acutal OD of hard AN sized tubing. The hose that fits over the tubing must have a snug fit, therefore the actual ID of the hose is somewhat smaller than the OD of the hard line. To find the acutal ID of the hose you're using, multiply the nominal ID of the hose by a factor of 7/8 [or 0.875]. This will give you the actual ID of the hose in inches. For a piece of 4-AN hose, the nominal ID is 1/4 inch, and the actual ID is [1/4 x 7/8] 7/32 inch.

AN hose's available sizes [at least that I am aware of] are 3, 4, 6, 8, 10, 12, 16, 20, and 24.

The respective nominal ID's are 3/16", 1/4", 3/8", 1/2", 5/8", 3/4", 1", 1 1/4", 1 1/2".

The respective actual ID's are 21/128", 7/32", 21/64", 7/16", 35/64", 21/32", 7/8", 1 3/32", 1 5/16" - though you may often find the ones with high denominators rounded to a fraction with a lower denominator.

Voila! Now you know how to properly size AN hose!


Modified by DaX at 4:01 PM 9/11/2008

 

Bomb information!!

 

You can get it bigger than -24 if you look hard enough. Not sure why you would need it though, coolant lines being the only thing that I can think of but not on a Honda. The hose shop here in town has -36 but they usually only stock about 10ft of it.