Inverted Flare Union 4pk 3/8in Line 5/8-18

The Inverted Flare Union 4-Pack 3/8-inch Line 5/8-18 from Allstar Performance is a vital fluid line connector designed for high-performance automotive systems, including fuel delivery circuits and hydraulic brake applications. These unions are essential for builders and mechanics who require reliable, leak-free connections under pressure and vibration, particularly when routing fuel lines, coolant passages, or brake circuits in modern engine bays or custom fabrication projects.

The inverted flare design creates a metal-to-metal seal that is more effective at resisting blow-out and weeping compared to standard compression fittings, especially under transient pressure spikes common in turbocharged or supercharged engines. The 3/8-inch line size is suitable for moderate fuel flow or coolant circulation without excessive restriction, while the 5/8-18 thread specification ensures compatibility with various applications.

This four-piece pack offers redundancy and flexibility for multi-line installations, making it an excellent choice for race car builders, engine swaps, and street performance applications where reliability is crucial. These unions are particularly beneficial for carbureted-to-EFI conversions and are designed to withstand the rigors of automotive environments.