The Siemens SENTRON 5SY6040-7 is a 1P+N miniature circuit breaker rated 40 A with a C-curve trip characteristic, breaking 6 kA per EN 60898 at 230 V AC. The 40 A rating at 30 °C derates to 38 A at 40 °C and 37.2 A at 45 °C, so if your panel runs hot, factor that in. The 1P+N pole configuration switches the line and switches the neutral but does not protect the neutral — it's a switched-neutral design, common in single-phase final circuits where you need isolation on both conductors.
Sealable, halogen-free, silicon-free construction suits environments where outgassing matters (clean rooms, medical, food processing). Touch protection is built in, so you don't need separate finger-safe shrouds on the terminals.