Author: Scott Bredemann
Updated: 03/14/2025 | Read Time: 3mins
If you’ve worked with fluid transfer systems in automotive, aerospace, or industrial applications, you’ve probably come across AN fittings and adapters. These precision-engineered connectors are known for their durability, high-pressure handling, and leak-free performance. Originally developed for military and aviation use, AN (Army-Navy) fittings have become the go-to choice for everything from high-performance fuel lines to hydraulic systems.
What are AN (Army Navy) Fittings?
AN fittings are designed with a 37-degree flare seat, which helps create a tight, reliable seal when connected. Unlike other types of fittings—such as NPT (National Pipe Thread), which relies on thread engagement for sealing—AN fittings use this flared design to prevent leaks and improve performance, especially in high-pressure environments. These fittings come in various sizes, indicated by a dash number (e.g., -4 AN, -6 AN), which corresponds to the outer diameter of the tube or hose they fit.
AN fittings are commonly made from aluminum, stainless steel, or brass, each offering different benefits depending on the application. Aluminum fittings are lightweight and corrosion-resistant, making them ideal for automotive and racing applications, while stainless steel versions provide extra strength and durability for high-pressure industrial and aerospace systems.
What are AN Adapters?
AN adapters serve as connectors that allow AN fittings to integrate with other thread types or hose styles. They are especially useful when modifying or upgrading a system that includes different types of fittings. Adapters come in various configurations, including:
- Thread adapters – Convert between AN threads and other standards like NPT, BSP, or metric.
- Reducer and expander adapters – Allow different AN sizes to be connected.
- Swivel adapters – Enable easier installation and adjustment by allowing rotation without breaking the seal.
- Bulkhead adapters – Pass through a panel or firewall to maintain a secure connection between lines.
AN Thread Sizes
Below is a table showing AN thread sizes, including the corresponding dash size, thread size, and the outer diameter (OD) of the tube it fits.
| AN Size | Thread Size (UNF) | Tube Outer Diameter (OD) |
| -2 AN | 5/16″-24 | 1/8″ (3.18mm) |
| -3 AN | 3/8″-24 | 3/16″ (4.76mm) |
| -4 AN | 7/16″-20 | 1/4″ (6.35mm) |
| -5 AN | 1/2″-20 | 5/16″ (7.94mm) |
| -6 AN | 9/16″-18 | 3/8″ (9.52mm) |
| -8 AN | 3/4″-16 | 1/2″ (12.7mm) |
| -10 AN | 7/8″-14 | 5/8″ (15.87mm) |
| -12 AN | 1-1/16″-12 | 3/4″ (19.05mm) |
| -16 AN | 1-5/16″-12 | 1″ (25.4mm) |
| -20 AN | 1-5/8″-12 | 1-1/4″ (31.75mm) |
| -24 AN | 1-7/8″-12 | 1-1/2″ (38.10mm) |
| -28 AN | 2-1/4″-12 | 1-3/4″ (44.45mm) |
| -32 AN | 2-1/2″-12 | 2″ (50.8mm) |
MISUMI USA carries a large array of Hydraulic Hoses & Fitings, including the following:
For questions on products related to NPT thread fittings, or any other product questions please connect with our product experts and engineers. And, for more articles on things related to industrial manufacturing and engineering check out more of our blog.