AN, NPT & Metric Fittings for Performance Builds

What This Category Covers

The Fittings collection covers the connective hardware that joins hoses, hard lines, and components across fuel, oil, cooling, brake, and forced induction plumbing. Fittings determine whether a fluid system stays leak free under the pressure, heat, and vibration loads found in performance street and race applications, so correct thread type and size selection matters as much as the hose or line itself.

What Is Included

AN hose ends (straight, 45 degree, 90 degree, 120 degree), swivel seat fittings, bulkhead unions, tee and union adapters, reducers, NPT to AN adapters, ORB adapters, metric port adapters, banjo fittings, weld bungs, port plugs, quick connect fittings, and crimp style hose ends.

AN Fitting Sizing and Standards

The AN standard, derived from Army-Navy aircraft specifications, uses a 37 degree flare seat and straight thread that provides a consistent, leak resistant connection across brands. Sizes are labeled by dash number, with -4 AN through -12 AN covering nearly all automotive fuel, oil, and hydraulic applications. Larger dash sizes flow more volume, so undersized fittings on a high output build create pressure drops that starve injectors, oil coolers, or intercoolers of adequate flow.

Common Dash Sizes

-3 AN and -4 AN for brake lines and small signal circuits, -6 AN and -8 AN for naturally aspirated fuel supply and oil feed lines, and -10 AN and -12 AN for boosted fuel systems, oil cooler circuits, and high volume return lines. Match dash size to the port thread on your pump, filter, regulator, or cooler before ordering an adapter.

NPT, ORB, and Metric Adapters

NPT pipe thread fittings seal by thread compression and are common on factory pump inlets, sensor bosses, and cast housings. ORB (O-ring boss) fittings seal with a static O-ring against a machined boss face and are common on aftermarket fuel rails and regulators. Metric fittings appear on European and Japanese platform ports. Thread to AN adapters convert any of these port styles to an AN hose end connection for a unified plumbing system.

Banjo Fittings and Weld Bungs

Banjo fittings route hose at a fixed angle from a bolt through a hollow banjo bolt, common on PCV catch can connections, brake calipers, and turbo oil feed lines. Weld in bungs let fabricators add a threaded port to a custom fuel cell, catch can, or intercooler end tank for a clean, leak free connection point.

Swivel and Adjustable Fittings

Swivel seat AN fittings rotate after installation so a line can be routed cleanly without twisting the hose or stressing it at a sharp angle. Adjustable angle hose ends let a fabricator dial in the exact routing angle needed in a tight engine bay, which is especially useful on turbo oil drain and feed lines where clearance is limited.

Top Fittings Brands

• Vibrant. Broad catalog of AN, NPT, and metric fittings, adapters, and port plugs
• Radium Engineering. Banjo fittings, ORB adapters, and OEM style quick connect fittings
• Fragola. AN hose ends and adapter fittings for fuel and oil systems
• Earl's. Swivel seat AN fittings and Speed-Seal hose ends
• Russell. AN fittings and Endura hose end lines
• Aeroquip. Aerospace derived AN fittings and adapters
• Fuelab. PTFE compatible swivel hose ends for E85 and racing fuel systems
• Nitrous Express. Nitrous system specific AN fittings and B-nuts
• Haltech. Weld in sensor bungs and fitting hardware
• Snow Performance. Water methanol reservoir bungs and quick connect fittings
• Mishimoto. Catch can fittings and adapter hardware
• Moroso. Oil pan stud kits and fitting hardware
• Exergy. Injector plugs and diesel fitting hardware
• Firestone. Push-lock air fittings for air suspension systems
• Aeromotive. Fuel system fittings and adapters for high flow pumps

How to Choose the Correct Fitting

• Confirm the port thread type on the component you are connecting to (AN, NPT, ORB, or metric)
• Match the dash size to your target flow rate and horsepower goal
• Verify male vs female thread and straight vs flared sealing surface
• Check fitting angle needed for clearance (straight, 45 degree, or 90 degree)
• Confirm swivel vs fixed orientation based on install access
• Use PTFE rated fittings with PTFE lined hose for E85 or racing fuel
• Apply thread sealant only on NPT connections, never on AN flare seats
• Torque fittings to spec, overtightening AN fittings can crack the flare seat
• Order matching hose ends and hose together to confirm compatible termination style
• Keep spare crush washers and O-rings on hand for banjo and ORB fittings

Common Questions

What is the difference between AN and NPT fittings?

AN fittings use a 37 degree flare cone that seals metal to metal against a matching seat, while NPT fittings use a tapered thread that seals through thread compression and sealant. AN fittings resist leaks better under high pressure and vibration and can be assembled and disassembled repeatedly without thread damage.

What size AN fitting do I need for my fuel system?

Naturally aspirated engines typically run fine on -6 AN supply lines, while boosted engines producing 500 to 900 horsepower generally need -8 AN, and the highest output applications step up to -10 AN or larger to prevent flow restriction under peak demand.

Can I mix fitting brands in one system?

Yes. AN fittings are a standardized thread and flare geometry, so fittings from Vibrant, Fragola, Earl's, Russell, and Aeroquip are interchangeable as long as the dash size and gender match.

Do I need PTFE fittings for E85?

Yes, for long term reliability. E85 degrades standard rubber hose over time, so PTFE lined hose paired with PTFE compatible fittings from Fuelab or Aeromotive resists ethanol breakdown better than standard fuel hose and fittings.

What is a banjo fitting used for?

A banjo fitting routes a hose at a fixed angle off a hollow bolt that passes through the banjo body, commonly used on brake calipers, turbo oil feed lines, and PCV catch can connections where a compact, rotatable connection is needed.

How do I convert an NPT port to an AN hose end?

Use an NPT to AN adapter fitting, threading the NPT side into the port with sealant and connecting the AN side to your hose end. This is the standard way to adapt factory pump and sensor ports to an aftermarket AN plumbing system.

Why is my fitting leaking after installation?

Common causes include a damaged or missing crush washer on ORB and banjo fittings, an undertightened or overtightened AN flare connection, mismatched thread types, or a hose end that was not fully seated before tightening. Inspect the sealing surface for damage before reinstalling.

What is a swivel fitting and when should I use one?

A swivel fitting allows the hose end to rotate after the fitting is tightened, letting you route the hose cleanly without twisting it. Use swivel fittings anywhere routing angle needs fine tuning after the fitting is torqued down, such as tight engine bay oil lines.

Do brake lines use the same fittings as fuel lines?

Brake systems typically use smaller -3 AN or -4 AN fittings sized for low volume hydraulic fluid flow. Oversized fittings in a brake circuit add unwanted fluid volume and increase pedal travel, so do not substitute fuel system dash sizes into a brake line.

What torque should I use on AN fittings?

Torque values vary by dash size and manufacturer, so check the specific fitting spec sheet. As a general rule, hand tighten until snug, then use a wrench to add roughly a quarter to half turn more. Overtightening can crack the flare seat or strip aluminum fitting threads.

Why Buy Fittings from Black Ops Auto Works

Black Ops Auto Works stocks 2,252 fitting SKUs across AN, NPT, ORB, and metric hardware with real fitment data, competitive pricing, and support from staff who plumb fuel, oil, and cooling systems themselves. Products are filterable by size, thread type, and application to confirm the correct fitting before ordering.

For focused shopping, browse our fuel delivery, cooling, braided lines, oil, and engine collections to complete your plumbing build.