The 300 A frame means the breaker body and bus connections are sized for that higher mechanical/thermal capacity, so this part handles a 25 A load with ample thermal headroom. Interrupting capacity hits 187 kA at 240 V, 121 kA at 415 V, and still 75.6 kA at 500 V, which puts it in the high-fault category for industrial mains or transformer-fed sub-distribution.
Occupies standard MCCB panel-mount cutout; front IP40 means the operator interface is protected against solid objects over 1 mm but not sealed against moisture — keep it inside an IP54 or better enclosure in washdown areas.