The Siemens SENTRON 5SL4163-6 is a 1-pole miniature circuit breaker rated 63 A at 30 °C with a B tripping characteristic — the magnet trip fires at 3 to 5 times rated current, so it's sized for resistive and general-purpose loads where you don't want nuisance trips from moderate inrush. The 10 kA breaking capacity per EN 60898 (also 10 kA per IEC 60947-2) means it can safely interrupt a fault up to 10,000 A at 400 V AC without welding its contacts or cascading upstream — that covers most residential and light-commercial service-entrance scenarios. Rated voltage is 400 V AC single-phase (250 V single-phase) and 440 V multi-phase, so it fits final subcircuits in a 230/400 V panel. The B-curve also means the breaker holds 63 A continuous at 30 °C, but derates to 58.21 A at 40 °C, 55.44 A at 45 °C, and 50.16 A at 55 °C — if the panel ambient runs hot, size the load side accordingly. Sealable (padlockable) handle is standard, letting you lock out a circuit for maintenance.
The 18 mm width occupies one modular unit — plan your rail layout accordingly.