Breaking capacity — the number that decides selectivity
This MCCB delivers 187 kA at 240 V AC, 121 kA at 415 V, 75.6 kA at 440 V, and 17 kA at both 500 V and 690 V. At 690 V the 17 kA rating still covers standard industrial motor circuits.
Thermal derating — don't assume 20 A at every panel temperature
At 60 °C it derates to 19 A, and it stays at 19 A through 70 °C. That matters for a continuous load near the breaker's nameplate.
That 76.2 mm width (3 inches) is the standard 3-pole MCCB footprint — it occupies three 25 mm DIN-rail module positions. The depth of 70 mm (2.76 in) leaves room for rear-mounted busbars or a panel gland plate without forcing an oversized enclosure.