AN Fitting Sizes Explained: 6AN vs 8AN vs 10AN

Quick answer

The dash number is the nominal hose or port size in sixteenths of an inch, so 6AN is 3/8 inch, 8AN is 1/2 inch, and 10AN is 5/8 inch. For most street fuel systems, 6AN and 8AN cover the feed side and 8AN or 10AN covers high-flow feed lines. Match the fitting to the hose and port you already have, then choose the smallest size that supports your flow target.

AN sizes confuse people because the number does not look like a measurement. It is: every dash number is the nominal inside diameter in sixteenths of an inch. That single rule answers most 6AN vs 8AN and 8AN vs 10AN questions before you open a catalog.

This comparison explains how 6AN, 8AN, and 10AN differ in practice, where an AN to NPT adapter or ORB adapter fits into the picture, and which size to buy for feed, return, and low-pressure lines. It uses DeatschWerks catalog facts for the fittings referenced below, and it flags where a specification is not supplied rather than guessing.

What the dash number actually means

AN sizing is nominal, not exact. A 6AN hose end is built around 3/8 inch nominal, an 8AN around 1/2 inch, and a 10AN around 5/8 inch. The number describes the hose or port it is designed to connect, not a measured outside diameter, so two 8AN parts from different brands can look slightly different while still sealing correctly.

This is why an AN fitting size chart is more useful than a ruler. Once you know the nominal size, you can compare a 6AN feed line to an 8AN feed line on flow area rather than appearance. The jump from 6AN to 8AN is a meaningful increase in cross-section; 8AN to 10AN is another step up, and each step changes how the line routes and how much space the fittings need.

• Remember the rule: dash number x 1/16 inch = nominal size.
• Measure the port or hose you are adapting to, not the wrench flat.

6AN vs 8AN: the common street comparison

6AN is the compact choice. It routes easily, weighs less, and works well for return lines, smaller feed lines, and tight engine bays where a 1/2-inch line would be awkward. If your fuel system is mild and your line runs are short, 6AN often does the job without adding bulk or cost.

8AN is the middle option and the one many enthusiasts default to for a feed line. It moves more volume than 6AN and still bends and routes without the space penalty of 10AN. The trade-off is real: 8AN hose and fittings are larger, heavier, and usually cost more, so stepping up only makes sense when your flow target or future plans justify it.

• Choose 6AN when packaging and simplicity matter more than maximum flow.
• Choose 8AN when you want headroom for a future upgrade without going to 10AN.

8AN vs 10AN: when the extra size pays off

10AN is for high-flow feed lines and applications where pressure drop matters. The larger nominal size reduces restriction, but it also demands more room, larger fittings, and more careful routing. In a cramped engine bay, a 10AN line can be harder to route cleanly than an 8AN line, and the fittings take up more space at every connection.

The honest trade-off is that 10AN is not automatically better. If your pump, regulator, and injectors do not need the volume, a 10AN feed line adds weight, cost, and packaging complexity for little gain. Step up to 10AN when your flow target, line length, or future plans clearly call for it, not because a larger number sounds stronger.

• Use 10AN when the feed line is long or the flow target is high.
• Stay with 8AN if the system is moderate and space is tight.

Where adapters and port threads fit in

AN hose ends do not connect directly to most factory ports. An AN to NPT adapter or an ORB adapter bridges the two thread systems, and the AN side still follows the dash-number rule. A 10AN ORB to 10AN Coupler, for example, connects a 10AN ORB male port to a 10AN male flare connection, so the AN side matches your 10AN line while the ORB side matches the port.

This is where size mistakes happen. People buy the right AN size but the wrong port thread, or they buy an adapter that changes the angle when a straight fitting would fit better. Check both ends before ordering: the AN dash number for the hose, and the port type for the component. If a specification is not listed, treat it as unknown and confirm before purchase.

• Confirm both ends: AN dash size on one side, port thread on the other.
• Use a swivel or angled fitting when routing needs it, not just for looks.

How to pick a size without overbuilding

Start with your flow target and your pump outlet, then work outward. If the pump outlet is a certain size, matching the feed line to it avoids an unnecessary step up or down. Return lines can usually be smaller than feed lines because they carry less volume. Low-pressure lines and gauge connections can be smaller still.

Then check the physical path. A 6AN line may fit where an 8AN line will not, and an 8AN line may fit where a 10AN line will not. The right answer is the smallest size that supports your flow and leaves a little headroom, not the largest size that fits in the catalog.

• Match the feed line to the pump outlet when possible.
• Size return and low-pressure lines smaller than the feed line.

Trade-offs to weigh before you buy

• 6AN: small and easy to route: Lower bulk, lower weight, and easier bends, but less flow headroom than 8AN or 10AN. Pick 6AN when packaging and simplicity matter more than maximum volume.
• 8AN: the middle ground: More flow than 6AN and easier to route than 10AN, but larger and more expensive than 6AN. Pick 8AN for a feed line that needs headroom without going to 10AN.
• 10AN: maximum flow, maximum space: Reduces restriction on high-flow feed lines, but demands more room and larger fittings throughout. Pick 10AN only when your flow target or line length clearly calls for it.
• Adapters: match both ends: An AN to NPT adapter or ORB adapter must match the AN dash size on one side and the port thread on the other. Verify the port type before ordering; if it is not listed, treat it as unknown.

Catalog facts for the fittings referenced

• 10AN ORB to 10AN Coupler: Connects a 10AN ORB male port to a 10AN male flare connection and is supplied with an O-ring in an anodized DW Titanium finish. Useful when a 10AN line must meet an ORB port; the included O-ring and the ORB-to-flare design remove the need for a separate sealing washer.
• 10AN ORB to 10AN Swivel: Built for fluid connection between a 10AN ORB port and a 10AN flare line with a low-profile 90-degree swivel configuration and an anodized DW Titanium finish. The 90-degree swivel helps route a 10AN line in tight spaces where a straight coupler would put the hose in the way.
• 8AN Male Flare Gauge Adapter with 1/8" Gauge Port: Provides a gauge connection point in an 8AN flare line with an 8AN male flare connection and a 1/8" gauge port. Lets you add a pressure gauge to an 8AN feed line without cutting in a separate tee, which keeps the line simpler.
• 10AN to 3/8" EFI Quick Disconnect: Adapts a 10AN female flare swivel to a 3/8" male EFI quick disconnect in an anodized DW Titanium finish. Bridges a 10AN line to a factory-style 3/8" quick disconnect, which is common when upgrading only part of a fuel system.

Which size should you choose?

Best for

• Street builds with mild fuel systems and tight engine bays that need compact routing
• Enthusiasts who want a feed line with headroom for a future upgrade without going to 10AN
• High-flow feed lines where pressure drop matters and space allows larger fittings

Not for

• Anyone who has not confirmed the port thread type on the component they are connecting to
• Builds that would gain nothing from a larger line but would lose routing space and add cost
• Buyers looking for an exact measured size rather than a nominal dash number

Match the AN dash number to your hose and port, pick the smallest size that supports your flow target, and confirm the port thread before you order. If you are unsure between two sizes, the smaller one usually routes better and the larger one only helps when your flow target truly needs it.