856A3339G02 is a precision aerospace component, compliant with AS9100D quality standards and FAA/EASA regulations, designed for the hydraulic systems of large commercial aircraft.

It acts as a hydraulic sequence valve seal ring, forming a high-precision, pressure-stable seal between the sequence valve's spool and valve body. This seal ensures the valve can accurately control the activation order of connected hydraulic subsystems, such as first activating the landing gear retraction, then the flap adjustment, avoiding misordered operation that would cause mechanical conflicts between aircraft components, reduce the coordination of system operation, or affect the safety of takeoff and landing processes.

Made from oil-resistant, high-pressure and high-temperature resistant fluorosilicone rubber, it operates stably at -45°C to 250°C, and resists long-term contact with aviation hydraulic fluids. Weighing 0.07kg, it allows fast MRO replacement, a key component for hydraulic system operation sequence reliability.