The C12E4TM125L is a Schneider Electric ComPacT NSXm 160E frame circuit breaker — a 4-pole, 125 A thermal-magnetic unit with a TM-D trip curve, built to EN/IEC 60947-2. That 16 kA figure is the performance level you'd check first for coordination with upstream gear.
At 108 mm wide (12 module pitches of 9 mm), 137 mm tall, and 80 mm deep, it takes up a standard 4-pole breaker footprint. Terminals are Everlink lugs on the front, both top and bottom, accepting 2.5 to 70 mm² flexible copper or 2.5 to 95 mm² rigid/stranded. With spreaders the connection pitch is 35 mm; without them, 27 mm. That's a beefy lug for a 125 A breaker — no adapter needed for larger feeder cables.