The Schneider Electric EZC250N44125 is a 4-pole EasyPact EZC250N circuit breaker with a thermal-magnetic TM-D trip unit, rated 125 A at 40 °C and delivering a 20 kA Icu breaking capacity at 440 V AC. It's built to IEC 60947-2 for distribution duty — the standard that governs molded-case breakers in commercial and industrial panels.
If your panel runs hotter — say 50 °C — the trip unit rating drops to 125 A at 50 °C, meaning the breaker still holds its full rating at that elevated ambient, no derate penalty. That's unusual for a thermal-magnetic; most need a size bump at 50 °C. Breaking capacity varies by voltage: 50 kA at 220–240 V AC, 25 kA at 380–415 V AC, 20 kA at 440 V AC, and 8 kA at 550 V AC. On the DC side, it's 20 kA at 125 V DC (1-pole) and 20 kA at 250 V DC (2-pole). That 690 V Ui tells you the internal creepage and clearance are designed for 690 V systems, even though the breaker's operational rating is 550 V.
This is a fixed-mount breaker on a backplate, not a DIN-rail snap-on. Connection pitch is 35 mm — standard for busbar or cable lug termination in a distribution board.