Its 125 A continuous current rating at 40 °C (derated to 114 A at 70 °C) covers feeder and main-switch duty for moderate-load subpanels, motor control centers, and building services. The interrupting capacity is voltage-dependent: 75.6 kA at 240 V, 52.5 kA at 415 V, 32 kA at 440 V, and 11.9 kA at both 500 V and 690 V. That means this breaker can clear high-fault scenarios on the secondary side of a 240/415 V transformer without cascading upstream — the 75.6 kA figure at 240 V is the one to check against your available fault current for 240 V delta or 208Y/120 V services.
The breaker holds its full 125 A rating from 40 °C up to 50 °C, then derates linearly to 114 A at 70 °C. For a panel that runs warm — say 55 °C inside the enclosure — you still get 122 A continuous, which is often enough to cover a 100 A feeder without upsizing the frame.
Width is 3 in, depth 2.76 in.