The 121 kA breaking capacity at 240 V gives serious fault-clearing headroom for high-available-fault panelboards or transformer secondaries, and it still holds 75.6 kA at 415 V and 52.5 kA at 440 V. That's the kind of interrupting rating that keeps selectivity intact downstream without cascading upstream breakers.
Thermal derating and ambient reality
At 55 °C it drops to 76.8 A, at 60 °C to 75.2 A, and at 65 °C to 73.6 A, bottoming at 72 A at 70 °C. That's a shallow curve; you lose only 10 % at the top of the operating range. If your panel sits near a kiln or a hot process line, you can still load it close to nameplate without oversizing.
Dimensions are 130 mm high, 76.2 mm wide, 70 mm deep — a compact 3-pole footprint that fits standard MCCB panel cutouts.