Bulkhead Nut #4

The FRAGOLA Bulkhead Nut #4 is a precision aluminum bulkhead fitting nut designed for AN-4 fluid system connections. This blue anodized fastener is engineered to securely seal and connect bulkhead fittings in high-pressure hydraulic, fuel, and coolant lines common in racing, aviation, and high-performance automotive applications. The AN-4 size accommodates quarter-inch nominal tubing, making it a versatile component for custom fluid routing systems.

Constructed from lightweight aluminum with blue anodized finish, this bulkhead nut resists corrosion while maintaining the low weight critical in performance applications. The anodized coating provides a protective barrier against oxidation in harsh environments—particularly important for systems exposed to fuel vapors, moisture, or salt air. The compact 1.05-inch diameter and 0.6-inch width allow integration into space-constrained engine bays and fuel cell compartments. FRAGOLA's manufacturing tolerances ensure consistent fit with standard AN-4 bulkhead fittings, eliminating gaps and potential leak points.

This bulkhead nut serves builders and technicians assembling custom fuel systems, hydraulic brake lines, coolant circuits, and transmission cooler plumbing. It is particularly suited for race car fabrication, marine engine installations, and restoration projects where AN-specification components are required for reliability and regulation compliance. Technicians value it as a replacement part when original fittings are damaged or when upgrading to larger-diameter tubing configurations that demand new fastening hardware.

The AN fitting standard ensures compatibility with FRAGOLA hose, adapters, and bulkhead fittings across the AN-4 product range. Whether you're building a fuel delivery system from scratch or replacing worn fasteners in an existing installation, this single nut supports system integrity and leak-free operation under vibration and pressure cycling.