390-04 -4 female tube nut

Speedflow SF390-04 | -4 AN Female Tube Nut | 37° Flare

The Speedflow SF390-04 is a precision-machined -4 AN female tube nut designed for use with 37° flared tubing in performance brake, fuel, oil, and hydraulic line assemblies. The tube nut threads onto a male AN fitting and clamps the flared tube end securely against the fitting seat, creating a leak-free metal-to-metal seal — the same proven connection method used throughout AN plumbing systems in motorsport and performance builds worldwide.

Product Specifications

• Part Number: SF390-04
• AN Size: -4 AN female
• Flare Requirement: 37° flare on tube end
• Type: Female tube nut
• Series: Speedflow 390 — AN Female Tube Nuts
• Compatible With: Standard -4 AN male fittings and 37° flared tubing
• Barcode: 9342122021114

Applications

The SF390-04 is an essential component for hard line and tube-based AN plumbing builds, including:

• Brake hard line connections to AN fittings and components
• Fuel hard line connections in custom fuel system builds
• Oil and hydraulic hard line assemblies in engine and chassis builds
• Replacing damaged or corroded OEM tube nuts with AN-compatible hardware
• Any application requiring a -4 AN female tube nut for 37° flared tubing

37° Flare — The AN Standard

The 37° flare is the defining characteristic of the AN (Army-Navy) plumbing standard and is distinct from the 45° flare used in some OEM and SAE applications. The tube nut works by threading onto the male AN fitting and drawing the 37° flared tube end tightly against the fitting’s matching cone seat, creating a reliable metal-to-metal seal without the need for sealants or gaskets. Always ensure your tubing is flared to exactly 37° before assembly — a 45° flare will not seal correctly in an AN fitting.

Sold individually. Requires 37° flare on the tube end. Compatible with standard -4 AN male fittings.