Straight Adapter Fitting #4 x 3/8 MPT

The Straight Adapter Fitting #4 x 3/8 MPT by FRAGOLA is a precision hydraulic and fuel line adapter designed for custom automotive cooling systems, fuel delivery upgrades, and high-performance engine builds. This fitting bridges two different port sizes seamlessly, allowing mechanics and enthusiasts to integrate aftermarket components with existing OEM infrastructure or adapt between competing system standards.

Built by FRAGOLA—a trusted name in motorsports plumbing for decades—this adapter handles the demanding pressures and temperature fluctuations found in street, track, and off-road applications. The #4 JIC (AN4) inlet connects to a 3/8-inch male pipe thread (MPT) outlet, making this straight adapter ideal for systems where lines must transition between SAE AN fittings and NPT threaded ports on radiators, water pumps, or fuel pressure regulators.

Mechanics installing custom cooling loops, turbocharger water lines, or fuel system upgrades will appreciate this adapter's compact 1.4-inch diameter profile and minimal weight (0.03 lbs) for tight spaces. The straight geometry eliminates stress points that elbow fittings create under vibration, reducing fatigue cracking in high-boost or supercharged applications. FRAGOLA's quality aluminum construction ensures lightweight performance without sacrificing durability, while the precise machining guarantees leak-free seals when paired with appropriate thread sealants or PTFE tape on the NPT side.