It's a DIN-rail mount, 36 mm wide (2 width units), and the 63 A rating means it handles high-demand loads like electric ranges or large subfeeds — not your typical lighting circuit. The 400 V AC rated voltage matches standard three-phase distribution in European and many Asian installations.
Depth is 76 mm. Accepts solid or stranded copper from 0.75 mm² to 25 mm². Screw terminals torque to 2.5 to 3 N·m.
The C characteristic (5-10x In magnetic trip) is the key selection parameter: it's meant for circuits where the load has some inrush, like small motors, transformers, or capacitor banks. If your circuit is purely resistive (heaters, incandescent lighting), a B-curve would give better protection. But for general-purpose branch circuits with mixed loads, C is the standard choice.