The Siemens 5SU1654-6KV25 is an FI/LS-protector — a combined residual-current device and miniature circuit breaker in one 1+N-pole unit, B characteristic, rated 25 A. The residual-current section is Type A, 300 mA sensitivity, with a 10 kA short-circuit capacity. The D=70 mm width matches the standard Siemens modular DIN-rail footprint, so it slots into a distribution board alongside other 70 mm-wide devices without extra adapters.
The 10 kA breaking capacity at 230/400 V is the standard domestic and light commercial fault level; if the prospective short-circuit current at the point of installation exceeds 10 kA, the device needs a back-up fuse or a higher-rated upstream breaker.