Single modular width (18 mm) on DIN rail, so it occupies one slot in a distribution board.
The 3 kA breaking capacity (IEC 60947-2) is the interrupting rating at 230/400 V AC; if your panel's available fault current exceeds that, step up to the 10 kA variants in the same SENTRON family. Single-pole switching on a 230 V phase-to-neutral circuit; for 400 V three-phase loads you'd need the 3-pole version. Rated for 50/60 Hz supply, single-phase up to 253 V or multi-phase up to 440 V. IP20 with conductors connected — finger-safe from the front, but not protected against dripping water. Mount in a closed distribution board or enclosure.
Snap-on DIN rail mount, any orientation. The 18 mm width (one modular unit) means 17 of these fit in a standard 18-module consumer unit. Mechanical life is rated 4,000 operating cycles, sufficient for a branch circuit breaker that sees infrequent switching.