#3 x #4 Male Reducer Fitting

The #3 x #4 Male Reducer Fitting from FRAGOLA is a precision AN adapter designed for custom fluid line systems where port sizes differ—a common requirement in modified engine builds, fuel system upgrades, and high-performance cooling circuits. This straight reducer fitting allows mechanics and fabricators to connect larger 4 AN lines to smaller 3 AN ports without requiring custom hose assemblies or problematic thread mismatches. Whether you're downsizing a fuel rail feed, adapting a turbo coolant circuit, or reconfiguring hydraulic brake lines in a custom chassis, this fitting solves real-world sizing conflicts that arise during engine swaps and performance modifications.

Machined from aluminum and finished in blue anodized coating, this male-to-male reducer maintains structural integrity while resisting corrosion in engine bay environments where moisture and heat exposure are constant. The straight configuration—no 45° or 90° bend—ensures minimal turbulence in fuel or coolant flow, critical for systems where pressure stability and consistent delivery matter. FRAGOLA's reputation in drag racing and street performance circles stems from exacting manufacturing tolerances; each fitting is precision-ported to ensure leak-free connections under pressure cycling and vibration. The compact dimensions (1.2 × 1.1 × 4.1 inches) and lightweight design (0.02 lbs) make installation straightforward in tight engine compartments without adding measurable weight to your build.

This adapter is essential for fabricators building custom fuel systems, coolant circuits, and brake lines where OEM hard lines don't align with aftermarket component ports. It's particularly valuable in LS engine swaps, turbocharged applications, and vintage restorations requiring modern AN plumbing. Pair it with matching hose and fittings in your system's AN size standard—verify port thread pitch before installation to ensure proper sealing. The blue anodized finish also serves as a visual identifier, helping you track system layout during complex builds where multiple adapters and fittings are in use.