Fuel rails are high-pressure conduits mounted to the engine’s intake manifold, distributing fuel to individual injectors. Constructed from metal or reinforced polymers, they feature precisely machined ports and O-ring sealing surfaces to maintain fuel integrity. Integrated fuel pressure regulators or provisions for external regulation maintain consistent delivery across all injectors. Modern rails often incorporate return or returnless fuel systems, impacting rail design and connection types. Materials must be fuel and temperature resistant to ensure longevity and prevent system failures.