What this MCB is and what the ratings mean for fit
The Siemens 5SL6250-8CC is a 2-pole miniature circuit breaker rated for 400 V with a 6 kA breaking capacity, a D tripping characteristic, and a 50 A current rating. The D-curve means it tolerates the high inrush currents typical of motor and transformer loads — it trips between 10x and 20x rated current, so it won't nuisance-trip on a compressor or conveyor start-up. The 6 kA breaking capacity at 400 V is the maximum fault current it can safely interrupt; it's sized for standard commercial and light industrial distribution boards where the prospective short-circuit current stays under that threshold.
Compliance documentation
The 5SL6250-8CC has been RoHS-compliant since 01 June 2013, and REACH candidate-list information is available on request. Export control classifications are AL: N / ECCN: N, meaning no special licensing is required for standard international shipments.