An AN fuel fitting is a type of fitting that is commonly used in automotive and aircraft applications to connect fuel lines, hoses, and other components of the fuel system. The term AN stands for Army-Navy, which refers to the military specification (MS) standard that these fittings conform to. AN fuel fittings are known for their precise thread sizes and tight seals, ensuring reliable connections in high-pressure fuel systems. They are commonly used in performance vehicles and racing applications due to their durability and resistance to leakage.