#4 Flare End Bulkhead Union Black

The #4 Flare End Bulkhead Union Black is a precision hydraulic and pneumatic fitting engineered for applications requiring reliable straight-through fluid transfer between two AN4 (quarter-inch) male connections through a panel or bulkhead wall. This AEROQUIP-manufactured component is essential for custom fluid system builds, aerospace applications, and high-pressure industrial setups where space constraints and vibration resistance demand a compact, male-to-male bulkhead design. Its black anodized aluminum construction provides both corrosion protection and a professional appearance across demanding environments.

Constructed from aluminum with black anodized finishing, this bulkhead union delivers durability and chemical resistance in fuel, oil, and coolant systems operating at elevated pressures. The flare-end design—characteristic of AN fittings—creates a mechanical seal through a 37-degree cone angle, eliminating the need for additional sealing compounds and ensuring leak-free performance under thermal cycling and vibration. The straight-through geometry allows fluid to pass through a bulkhead panel without path obstructions, making it ideal for retrofit installations and OEM applications where system efficiency is critical. At just 0.05 lbs and compact dimensions of 2.3 x 1.1 x 3.75 inches, the fitting integrates seamlessly into tight-package system layouts without sacrificing structural integrity.

Aircraft builders, motorsports fabricators, and industrial hydraulic technicians rely on AEROQUIP bulkhead unions for consistent performance and compatibility across fluid systems. Installation requires two AN4 male ports with matching flare-end adapters or hose assemblies; the union itself threads into the bulkhead opening and accommodates standard -4AN tubing and hose with JIC or NPT adapters. Whether you're assembling a fuel injection system, building custom cooling circuits, or repairing industrial equipment, this bulkhead union meets aerospace material specifications and delivers the reliability expected from AEROQUIP's heritage in mission-critical applications.