AN Fitting Sizes Explained: The Complete NZ Guide (With Chart)
The Partsman
If you have ever stared at a wall of fittings wondering what "-6 AN" actually means, you are not alone. AN sizing trips up a lot of people. Here is the plain-English version, plus a size chart you can bookmark.
What does "AN" mean?
AN stands for Army-Navy, a sizing standard that came out of the US military. It describes the outside diameter of the tube the fitting suits, measured in 1/16" steps. So a -6 AN fitting relates to 6/16" (3/8") tube. The number after the dash is the "dash size".
AN size chart
| Dash size | Tube OD | Typical use |
|---|---|---|
| -3 | 3/16" | Brake lines, gauge lines |
| -4 | 1/4" | Oil pressure, small fuel feed |
| -6 | 3/8" | Fuel feed, oil cooler lines |
| -8 | 1/2" | Fuel feed/return, oil |
| -10 | 5/8" | High-flow fuel, oil drains |
| -12 | 3/4" | Turbo oil drain, big fuel |
| -16 | 1" | Coolant, breathers |
| -20 | 1-1/4" | Radiator, large coolant |
Threads: AN, ORB, NPT and BSP
AN fittings seal on a 37-degree flare, not the thread. You will also run into ORB (O-ring boss) for ports, and pipe threads like NPT (American) and BSP (British) on pumps, regulators and blocks. Adapters let you go from one to another, which is why a good fittings drawer has a few on hand.
How to choose the right size
- Match the dash size to your flow needs - bigger is not always better; oversizing a return line can drop pressure.
- Check the thread on whatever you are connecting to (pump, reg, rail).
- Pair fittings with the matching hose series (100, 200, push-lock).
Need a hand matching sizes? We have 30+ years on the tools - call us on 07 846 1923 or shop AN fittings & adapters. We can also fit hose ends to your braided hose for you.
