The 45 mm width means it takes one standard module slot in a panel — no surprises when laying out a row of breakers. IP20 on the front, so it's protected against finger contact once the panel door is closed.
The 4 A continuous rating sets the motor FLA it can carry without nuisance tripping. Breaking capacity holds at 100 kA up through 500 V AC, dropping to 6 kA at 690 V AC; at 400 V, that 100 kA covers virtually any industrial fault level you'll find downstream of a distribution transformer. The 1.5 kW motor power rating at 400 V gives a quick sizing reference for three-phase squirrel-cage motors.
The main circuit accepts solid conductors from 0.5 to 1.5 mm² (two per clamp) or 0.75 to 2.5 mm² (two per clamp); stranded goes up to 2.5 mm² (two per clamp) or 2.5 to 6 mm² (two per clamp). That covers most motor branch circuit wiring up to about 4 mm² for the feed. Auxiliary switch contacts are rated 1 A at 24 V, 0.5 A at 230 V, and 0.15 A at 60 V — enough for a PLC input or a contactor coil.