The C16B6TM125C is a 4-pole ComPacT NSX 160B moulded-case circuit breaker from Schneider Electric, fitted with a TM-D thermal-magnetic trip unit rated 125 A at 50 °C.
This breaker carries a 'B' breaking capacity code — 25 kA Icu at 380/415 V AC, 20 kA at 440 V, and 40 kA at 220/240 V. On a 415 V supply that's enough for most distribution boards downstream of a transformer; you get full selectivity with upstream gear rated above that. The thermal-magnetic TM-D trip handles overloads (L) thermally and short-circuits (I) magnetically — no electronics to fail, no auxiliary power needed.
Schneider lists the C16B6TM125C as current production. The 125 A TM-D trip is a common spare for NSX160B frames.
Backplate-mounted, flat on the back, horizontal or vertical orientation — no DIN-rail clip on this MCCB, so plan for panel-mount hardware. Front connections both top and bottom, 35 mm connection pitch. The 4-pole version (neutral left, no protection on neutral — 3D setting) fits a 140 mm wide footprint, 161 mm tall, 86 mm deep. IP40 enclosure, IK07 impact rating; pollution degree 3 means it's fine in a standard industrial panel with some conductive dust.