Fittings

Fittings and AN fittings are a popular solution in motorsport, tuning, and custom-built cars where higher demands are placed on durability, flow, installation, and flexibility than with standard fittings and hoses. At Qualitec, you will find a wide range of fittings for fuel systems, oil systems, catch can solutions, cooling systems, and other high-performance applications where a strong and leak-free connection is important.

AN fittings are often used in both motorsport and performance builds because they make it possible to create more professional and service-friendly hose systems. They are suitable for fuel hoses, oil hoses and other installations where a reliable solution with a nice finish and good function is wanted. In addition, the AN system is known for its good flow and flexibility, which is one of the reasons why this type of fitting has also been used in the aircraft industry and other demanding technical environments.

At Qualitec, we stock many different types of AN fittings in several sizes, angles and designs, so you can more easily put together the solution that suits your exact project. Whether you need fittings for fuel, oil or other fluids, AN fittings are often the obvious choice when you want to build a neat, strong and functional system. In many cases, adapters or nipple fittings are also needed together with the AN fitting itself, so the installation fits the components on the car correctly. Several models are also made with a swivel function and O-rings, allowing the hose to rotate freely 360 degrees. This makes installation easier and reduces the risk of the hose being twisted or ending up in an unsuitable position once the fitting has been tightened.

Installing AN fittings is in many cases relatively simple. The hose is cut to the desired length, the fitting is mounted onto the end of the hose, and the socket is tightened so the connection becomes secure and ready for use. Although special tools are not always required, it is often a major advantage to use suitable spanners during installation so the anodised surface is not damaged. It can also be a good idea to secure the hoses correctly with, for example, aluminium line separators, so the installation becomes both neater and more stable. Also see our thread chart for AN fittings to learn more about AN fittings and thread types.

Frequently asked questions about AN fittings (click to open)

What does “AN” mean in AN fittings?

“AN” means Army–Navy and comes from a U.S. military standard. AN fittings are 37° flare couplings for fluids/oils in hoses and tubes.

What does 6AN / AN-6 mean in practice?

The dash size historically tracks outside tube diameter in sixteenths of an inch (-6 = 6 × 1/16" = 3/8"). Actual hose ID/OD varies by hose type and manufacturer.

How do I convert AN sizes to mm?

Rule of thumb: AN-6 ≈ 3/8" (about 9.5 mm tube OD). Always check a sizing table, as hose ID differs by construction — AN is not a strict “mm standard”.

Are AN and JIC the same — and can they be mixed?

Both use a 37° flare and look similar, but AN (mil-spec/aviation) and JIC (industrial/SAE J514) can differ in tolerances and material specs. They may appear compatible, but avoid mixing them in critical systems.

What’s the difference between AN flare and NPT?

AN/JIC seal metal-to-metal at the 37° flare seat. NPT is a tapered pipe thread that seals in the threads and typically needs a thread sealant.

Do I need thread tape/sealant?

AN/JIC 37° flare: No — sealing is at the flare seat, not in the threads.
NPT/NPTF/BSPT: Yes — tapered pipe threads usually require sealant (exceptions exist, e.g. NPTF “dryseal”).

Can I screw NPT directly into an AN fitting?

No. AN is a 37° flare; NPT is a tapered pipe thread — two different systems. Use the correct adapter (e.g., AN ↔ NPT).

Is British pipe thread (BSP) the same as NPT?

No. BSP uses a 55° thread angle; NPT is 60°. They are not interchangeable. Use BSP↔NPT adapters when crossing standards.

What about ORB (O-ring Boss) vs AN?

ORB (SAE J1926) seals with an O-ring in a parallel UN/UNF port. AN seals at 37° flare faces. Adapters exist between the two systems.

Which AN size is typically used for…? (guideline — verify for your setup)

Brakes/clutch: AN-3 / AN-4
Oil feed (turbo): AN-4
Fuel feed (supply): AN-6 / AN-8 / AN-10
Fuel return: AN-6 / AN-8 / AN-10 (often same as feed)
Oil cooler: AN-10
Power steering/coolers etc.: AN-6 / AN-8 / AN-10 depending on flow

Which hose should I use for pump petrol, E85, methanol, etc.?

PTFE-lined AN hose is highly chemical-resistant (petrol, alcohol/E85, oil, coolant) with very low permeation — a solid “fit-and-forget” choice.
Rubber/CPE hoses can work, but service life/odour/permeation depend on the compound. Use only types the manufacturer rates for E85/alcohol.

What are “high-flow” 45°/90°/120°/150°/180° AN fittings — do they increase flow?

“High-flow” variants use a larger bend radius and internal passage to cut pressure drop in tight bends. Use the largest practical bend and avoid unnecessary series of 90° elbows for the best flow.

How do I identify my thread type (AN/JIC, NPT/NPTF, BSPP/BSPT, ORB)?

Check if the thread is tapered (conical) or parallel.
Measure pitch and diameter.
Note the sealing method (flare/O-ring/thread). Parker offers a handy 4-step ID guide.

Assembly: how tight should an AN joint be?

Tighten to first seat contact, then a controlled number of flats (hex sides). Do not over-tighten; use proper spanners to protect the anodising.

Why is my AN assembly leaking? (3-step troubleshooting)

Inspect flare faces for scratches/burrs and confirm the 37° angle.
Check hose length/bend radius — overly tight bends can load the joint.
Verify hose type and end: PTFE hoses require the correct olive/ferrule.

Are AN and A/C (air-conditioning) fittings interchangeable?

No. A/C systems use different O-ring/face-seal geometries and refrigerants. Use fittings designed specifically for A/C.

Quick terminology

AN/JIC 37° flare: metal-to-metal seal at the cone.
NPT/NPTF: tapered pipe thread; usually needs sealant.
BSPP/BSPT: British pipe threads (55°); not compatible with NPT (60°).
ORB (O-ring Boss): parallel UN/UNF thread with an O-ring in the port.

Size & application guide (AN-3 to AN-12)

Note: AN is a 37° flare system — not a millimetre standard. Use this as a rule of thumb and always verify against hose/component data (ID, pressure, temperature, and fluid compatibility).

AN-3 — Brake hoses & clutch (hydraulic)

Typical systems: Brake lines, clutch
Notes: High pressure, small volume. Often hardline or PTFE-lined brake hose.
Relevant categories: Brake fittings · PTFE hose · Hardline & adapters

AN-4 — Turbo oil feed, small oil lines, clutch

Typical systems: Turbo oil feed, small oil lines, clutch
Notes: Metered feeds; use a restrictor if specified by the turbo manufacturer.

AN-5 — Niche size

Typical systems: When 4AN is too small and 6AN too large
Notes: Check accessory compatibility/availability
Relevant categories: Adapters

AN-6 — Fuel return, moderate flow (EFI/street)

Typical systems: Fuel return, moderate flow
Notes: Very common. For E85/methanol, a PTFE-lined hose is typically recommended.
Relevant categories: AN fittings · PTFE hose · Fuel components

AN-8 — Main fuel feed (EFI), oil cooler, catch can

Typical systems: Main fuel feed, oil cooler, catch can
Notes: Higher flow than 6AN; lower pressure drop on longer runs and at higher power.
Relevant categories: High-flow fittings · Oil cooler parts

AN-10 — Oil systems, turbo oil return, high-power fuel

Typical systems: Oil systems, turbo oil return, high-power fuel
Notes: Widely used for turbo oil return and oil cooler circuits. Use gentle bends (45–90°) for best flow.
Relevant categories: High-flow 90° · Oil system

AN-12 — Tank → pump (lift/surge), dry-sump feed/return, large vents/breathers

Typical systems: Tank → pump (lift/surge), dry-sump feed/return, large breather/vent lines
Notes: Very high flow; needs ample space and matching ports/fittings.
Relevant categories: Tank fittings · Large bends

Practical tips

Hose type: For E85/methanol, choose PTFE-lined hose for low permeation and longevity.
Bends: Use the largest practical bend (45/60/90/120/150/180°) and avoid multiple sharp 90° bends in series.
Standards: AN/JIC (37° flare) ≠ NPT/BSP/ORB. Always use the correct adapters.
Verify data: Check the manufacturer’s flow, pressure and temperature ratings for your parts.