5mm ceramic ferrule — the same diameter as SC and ST connectors — to hold and align the fiber. The defining feature is the threaded coupling nut that screws onto the mating adapter, providing a secure, vibration-resistant connection. FC connectors are used in datacom, telecommunications, measurement. JIS, IEC standard compliant and intermateability test certified. Comply with IEC 61754-13 and JIS C 5970(type F01). Available with PC polishing, advanced PC(AdPC) polishiing and Angled PC(APC) polishing. Satisfies flammability rating UL94V-0. Designed for precision test equipment, single mode networks, and high-vibration environments. IEC 61754-13 · TIA-604-4 (FOCIS 4) · Telcordia GR-326. How the FC fiber connector works: screw-lock mechanism, PC vs APC polish, specs, and comparison with LC and SC connectors.