The Siemens 5SY6250-8 is a 2-pole SENTRON miniature circuit breaker rated 50 A at 400 V AC, with a D tripping characteristic. The 6 kA breaking capacity per EN 60898 covers standard domestic/commercial fault levels; the 10 kA per IEC 60947-2 covers industrial panels where higher prospective fault current is expected. It also carries a 5 kA rating per UL 1077 and CSA C22.2 No. 235, so it's accepted in North American control-panel applications.
Mounting position is any, so vertical or horizontal busbar feeds work. Depth is 76 mm, installation depth 70 mm; that's standard for the SENTRON 5SY6 family, so it fits existing panel layouts without re-spacing.