The Siemens 5SL3450-7MB is a 4-pole miniature circuit breaker rated for 400V AC with a 4.5kA breaking capacity, a C-curve trip characteristic, and a 50A rated current. It belongs to the Basic Devices product family within the 5SL series.
Packaged singly, dimensions 216 x 93 x 82 mm. The 4-pole form factor occupies four standard DIN-rail module widths (roughly 72 mm total). In a crowded enclosure, account for the 50A rating's thermal dissipation — adjacent devices may need derating if ambient exceeds 40°C. The C-curve's 5-10x In trip band means it coordinates well with upstream Type S or selective breakers for branch-circuit selectivity.