The TE Connectivity 5504407-4 is an FC-to-FC simplex coupler — a bulkhead adapter that joins two FC-terminated singlemode patch cables. Both adapter ends are FC receptacles, making this a female-to-female pass-through for in-line splicing or panel routing. The housing is machined brass with a silver finish, and the alignment sleeve uses a zirconia ferrule, the standard choice for singlemode FC connections where insertion loss and return loss stability matter.
Mounts in a panel cutout with a bulkhead nut — the brass body provides mechanical rigidity and the dust cap keeps the ferrule sleeve clean when the port is idle. The simplex format handles one fiber per coupler; for duplex runs you'd use two side-by-side.