#12 O-Ring Boss Plug

The AEROQUIP #12 O-Ring Boss Plug (FCM3727) is a hex-head aluminum fitting designed for hydraulic and pneumatic systems that demand reliable port closure. This AN-12 O-ring boss plug features blue anodized finish for corrosion resistance and uses an elastomer O-ring seal to prevent fluid leakage in pressurized applications. It's engineered to mate with standard AN-12 O-ring boss ports found in aircraft, automotive, industrial, and marine hydraulic assemblies.

The hex head design enables straightforward installation and removal using standard wrenches. AEROQUIP's aluminum construction with anodized coating balances weight reduction against corrosion protection—critical in environments where steel fittings would oxidize. The O-ring seal creates a positive, reusable closure that maintains system integrity across pressure cycles without requiring thread sealant tape or additional sealing compounds. The AN-12 sizing indicates the nominal 3/4-inch port diameter, a common specification in mid-size hydraulic systems where flow rate and pressure capacity align with typical industrial and mobile equipment requirements.

This plug serves technicians and engineers maintaining or assembling closed hydraulic circuits where a temporary or permanent port seal is needed. It's frequently used in equipment servicing, system testing, and assembly of custom hydraulic manifolds. The blue anodized finish provides visual identification and UV-resistant protection suitable for both indoor shops and outdoor equipment storage. Its compact dimensions make it suitable for tight-clearance applications where space constraints limit fitting options.

AEROQUIP is recognized for precision hydraulic fittings that meet or exceed SAE (Society of Automotive Engineers) specifications for AN-series components. This O-ring boss fitting adheres to ORB (O-Ring Boss) port geometry standards, ensuring compatibility across manufacturers and applications. When purchasing AN hydraulic fittings, confirming the correct port style—ORB versus NPT versus JIC—is essential to avoid incompatible connections that can compromise system performance.