4AN Female to 6AN Male Aluminum Flare Reducer Fitting Adapter for Automotive Fuel Systems

We've been running these in our own builds for a while now, and they hold up well under standard fuel system pressures—nothing exotic, but the 300 PSI working pressure covers most street and moderate track use. It's a straight 4AN female to 6AN male flare reducer, black anodized alumnum, CNC machined with that nice tight threading that doesn't bind up too much during assembly.

Basically, if you're plumbing a fuel system where you need to step down from a larger line to a smaller fitting—like going from a 6AN hose to a 4AN rail inlet—this is the piece. Most buyers go with the 4AN to 6AN size for oil cooler lines or brake line adapters, actually, because of that it's a common reducer scenario that avoids having to buy a separate adapter hose.

It's not for high-pressrue brake systems above 300 PSI or anything with a swivel requirment—this one's a solid straight fitting with no O-rings, so you'll need to use thread sealant or an appropriate flare seal. Teh anodizing is decent but can chip if you overtighten, so go easy.

Tempearture range is -40°F to 300°F, so it's fine for engine bays but don't run it on a turbo oil return line that sees sustained heat near that upper limit. We usually have stock in multiples of 10 or so, but confirm lead time if you're ordering 50 units or more—sometimes CNC batches take 20 days or so.

One detail a lot of folks miss: the 4AN female end has a standard 37° flare seat, which means it'll mate with any 4AN male flare fitting, but the 6AN male end needs a 6AN female flare nut or hose end (check your existing setup). It's better than some of the cheaper cast fittings we've seen—tighter tolerance on the threads, less chance of galling.