#4 x 7/16-20 (#4) Radius O-Ring Fitting Black

The #4 x 7/16-20 (#4) Radius O-Ring Fitting Black is a precision hydraulic and pneumatic adapter designed for professionals who demand reliability in fluid transfer systems. This straight adapter connects two #4 AN (Army-Navy) male ports, making it essential for fuel systems, brake lines, and custom hydraulic builds where secure, leak-free connections are non-negotiable. Built by FRAGOLA, a trusted manufacturer in the fluid transfer industry, this fitting serves motorsports enthusiasts, industrial technicians, and aerospace applications where performance and safety intersect.

Engineered from aluminum and finished in black anodized coating, the #4 x 7/16-20 fitting utilizes an O-ring seal design that eliminates the need for thread-sealing tape or paste, providing superior vibration resistance and reducing connection failure risk. The radius O-ring design—a FRAGOLA hallmark—distributes sealing pressure evenly across the connection face, preventing galling and ensuring consistent performance across pressure cycles. The 7/16-20 thread pitch is the industry standard for #4 AN fittings, guaranteeing compatibility with any spec-compliant hydraulic component. Anodized aluminum construction balances lightweight durability with corrosion resistance, ideal for both engine bay and exposed outdoor installations.

This fitting is ideal for drag racers, hot rodders, and custom builders integrating or repairing fuel, oil, or coolant systems where AN connections are the gold standard. Installation is straightforward—thread both male ports hand-tight, then snug with a wrench; the O-ring seal is self-contained, requiring no additional sealant. Weighing only 0.02 lbs, it adds negligible mass to any system while maintaining the structural integrity required for pressurized applications. Whether you're upgrading a vintage muscle car, maintaining a race vehicle, or fabricating a high-performance build, this FRAGOLA adapter delivers the precision fit and durability that separates amateur and professional results.