Its interrupting capacity hits 330 kA at 240 V AC, 242 kA at 415 V, and 187 kA at 500 V — numbers that tell you it can clear a high-fault bolted short without venting the panel. The 400 A frame carries a continuous rating that holds flat from 40 °C up to 50 °C (still 400 A), then derates linearly to 340 A at 70 °C; if your enclosure runs hot, that 340 A ceiling is the real limit, not the nameplate 400 A. No ground-fault monitoring built in — that is handled separately if your installation requires it.
That 138 mm width is a three-pole MCCB on a standard DIN-rail or bolt-on mount — verify the bus-bar spacing in your existing panel; it will not drop into a panel cut for a 3VA1110 frame without checking the mounting centres. Power loss is 98.5 W maximum at rated load. That is heat that stays inside the enclosure — account for it in your thermal budget, especially if the breaker sits near sensitive electronics or in a sealed cabinet.