The Mitsubishi QC12B is a Q Series extension base unit connection cable, 1.2 m long, used to link base units in a MELSEC Q PLC rack. This cable carries the signal bus between the main base unit and an extension base unit, letting you expand the I/O count beyond a single rack without adding a separate network interface.
Typical lead time for the QC12B runs 1 to 10 working days, which suggests it is a stocked line item rather than a build-to-order part.
The 1.2 m length is the standard reach between adjacent or near-adjacent base units in a panel; longer runs would need a different order code from the Q series extension cable family.