Fitting 5/16in Tube to 3/8in Barb

The 5/16in Tube to 3/8in Barb Fitting from DERALE is an essential adapter for custom cooling system configurations, designed specifically for mechanics and enthusiasts upgrading radiator hoses, auxiliary coolers, and fluid transfer lines. Whether you're fabricating a custom engine bay layout, installing an aftermarket transmission cooler, or rerouting coolant pathways on a heavily modified engine, this fitting bridges the critical size gap between 5/16-inch tubing and 3/8-inch barbed connections. It's a staple for serious build work where OEM hose routing won't accommodate your performance upgrades or custom plumbing requirements.

This compact adapter features a 5/16-inch tube inlet that accepts standard fuel or coolant line, mated to a robust 3/8-inch barb outlet designed to grip braided hose with positive retention—no clamps required, though quality stainless hose clamps are recommended for safety-critical cooling circuits. The barbed design creates a mechanical lock that resists vibration-induced loosening common in engine compartments, making it ideal for high-performance or racing environments where system integrity is non-negotiable. Measuring just 2.75 x 1.3 x 3.95 inches and weighing a mere 0.05 lbs, the fitting integrates seamlessly into tight engine bays without adding bulk or complexity to your plumbing layout.

Professionals and DIY builders rely on this fitting for coolant bypass lines, remote oil cooler installations, intercooler plumbing, and auxiliary water pump circuits on LS swaps, turbocharged builds, and liquid-cooled supercharger systems. The adapter accommodates both braided nylon and reinforced rubber hoses, making it compatible with aftermarket cooling components from major manufacturers. Installation is straightforward—insert the 5/16-inch tube end into your source line (use a barb sizing tool if needed for precision fit), and connect the 3/8-inch barb to your destination hose with appropriate clamps, ensuring your custom cooling system operates safely under sustained load and temperature cycling.