#3 O-Ring Boss Plug

The AEROQUIP #3 O-Ring Boss Plug (FCM3722) is a precision hydraulic fitting designed to seal open ports in fluid power systems. This hex head aluminum plug features an integrated O-ring seal and blue anodized finish, making it the ideal choice for sealing 3 AN (AN3) connections where flow termination is required. The O-ring boss design ensures positive sealing across a wide range of operating pressures and temperatures without relying on tape or paste.

Constructed from aluminum and finished with blue anodization, this fitting delivers corrosion resistance suitable for both mobile and stationary hydraulic installations. The hex head profile provides secure gripping for wrench engagement during installation and removal. The O-ring sealing element eliminates the need for thread sealant, reducing assembly time and minimizing contamination risk in fluid power circuits. This design meets the AN (Air Force-Navy) standard specification for interchangeability and performance, ensuring compatibility with any equipment manufactured to 3 AN hydraulic specifications.

Technicians and maintenance personnel working with closed-loop hydraulic systems, aerospace components, agricultural equipment, and industrial machinery rely on O-ring boss plugs to safely cap unused AN ports. Proper sealing prevents fluid loss, contamination ingress, and system pressure degradation. The AEROQUIP FCM3722 is commonly stocked as a replacement part and repair component in mobile hydraulic service trucks and maintenance facilities. Its compact size and standard 3 AN thread compatibility make it a universal solution across multiple equipment platforms.

AEROQUIP, a Parker Hannifin subsidiary, has established itself as a primary manufacturer of hydraulic hose assemblies and fluid connectors for demanding industrial, mobile, and aerospace applications. O-ring boss fittings remain the industry standard for sealed hydraulic connections where vibration, pressure cycling, and thermal expansion require dependable, leak-free performance.