At 240 V AC it is rated 100 kA — that covers most secondary substations and large distribution panels. At 400 V AC it drops to 25 kA, still enough for typical motor control centers. Motor ratings are given in horsepower for common North American voltages: 3 hp at 230 V, 5 hp at 200/208 V, 7.5 hp at 220/230 V, and 15 hp at 460/480 V. For 400 V three-phase systems (common outside North America), the breaker is rated 25 A. The fuse backup recommendations are gL/gG 63 A at 400 V, 50 A at 500 V and 690 V — these are the maximum fuse sizes that still allow the breaker to clear a fault within its rated breaking capacity.
The 45 mm width (three 15 mm modules) is the standard footprint for this current range — it occupies the same slot as a contactor of similar rating.