The Siemens 5SJ6516-7KS is a SENTRON 5SJ6 miniature circuit breaker (MCB), 1-pole plus neutral (1P+N), rated 16 A with a C-curve trip characteristic. It breaks fault currents up to 6 kA per EN 60898 and IEC 60947-2 at 230 V AC. The 2-module-width (36 mm) body fits standard DIN-rail enclosures; the 76 mm depth leaves room for wiring behind the panel.
The 16 A rating at 230 V AC covers most branch circuits in residential and light-commercial panels. The 6 kA breaking capacity matches the typical prospective short-circuit current at the service entrance of a building wired per IEC 60364; if your fault level is higher, you'd step up to a 10 kA or 15 kA rated MCB.