Breaking capacity is the headline: 187 kA at 240 V, 121 kA at 415 V, 75.6 kA at 440 V, and 17 kA at 500 V and 690 V. Power loss maxes at 10.8 W.
At 55 °C it drops to 39 A, at 65 °C to 38 A, and at 70 °C to 37 A. That's a shallow derating curve — you can push ambient to 50 °C without losing ampacity, which buys you flexibility in a warm panel or near a heat source.
That 101.6 mm width is exactly 4 inches. Front protection is IP40 — no ingress of tools or wires larger than 1 mm, but not sealed against dust or water.