Its 400 A continuous current rating (at 40 °C through 50 °C) and 3-pole design suit it for main feeder or large branch protection in 3-phase systems up to 690 V. Interrupting capacity is 330 kA at 240 V, 242 kA at 415 V and 440 V, 187 kA at 500 V, and 7.5 kA at 690 V — so it can handle high fault currents on the low-voltage side of a transformer, but derates sharply above 500 V. Thermal derating starts at 55 °C: 385 A at 55 °C, 370 A at 60 °C, 355 A at 65 °C, 340 A at 70 °C.
That depth (4.33 in) is the body-only dimension — allow additional clearance for the shunt trip (STL) and the auxiliary switch block (2 aux + 1 trip alarm HQ) fitted as standard on this order code. In a sealed, low-ventilation enclosure, that heat has to be factored into the thermal budget — especially if multiple breakers are ganged.