856A2978G01 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 relief valve seal ring, forming a tight, pressure-resistant seal between the relief valve's plunger and valve body. This seal ensures the valve can accurately release excess hydraulic pressure when the system reaches the preset threshold, preventing overpressure that would damage hydraulic components, disrupt the operation of flight control or landing gear systems, and create flight safety hazards.

Made from oil-resistant, high-temperature and pressure-resistant fluorosilicone rubber, it can work stably at -45°C to 245°C, and resists long-term contact with aviation hydraulic fluids. Weighing 0.07kg, it enables fast replacement during MRO, a critical component for hydraulic system pressure protection.