A Tube x AN Union fitting is used to connect a tube to an AN (Army-Navy) standard fitting. 

Tube x AN Union:

• Design: This fitting typically features a straight design where one end is designed to connect to a tube and the other end has AN threads.
• Connections: The tube end connects to the tube using a compression fitting or similar method, ensuring a secure, leak-proof seal. The AN end has standard AN threads that are designed to connect to other AN fittings or components, often used in aerospace and high-performance automotive applications.
• AN Threads: AN fittings are known for their high-performance and are commonly used in systems requiring robust, vibration-resistant connections.
• Usage: Frequently used in high-pressure and high-temperature applications such as fuel lines, hydraulic systems, and in aerospace industries, where a reliable connection between tubing and AN fittings is required.

This fitting provides a secure and efficient way to transition between tubing and AN standard components, ensuring compatibility and performance in demanding environments.