The Siemens SENTRON 5SL1116-7MB is a 1-pole miniature circuit breaker (MCB) with a C tripping characteristic, rated 16 A at 230 V single-phase and 440 V multi-phase AC, 50/60 Hz. The 3 kA breaking capacity per IEC 60947-2 tells you it can safely interrupt a fault current up to 3 kA at 230/400 V without welding its contacts or cascading failure upstream. That's adequate for most sub-distribution boards fed by a transformer with limited fault current; if your available fault current exceeds 3 kA, step up to the 10 kA-rated SENTRON siblings.
The 18 mm width means it takes up one slot in a multi-row consumer unit or sub-panel, leaving room for additional circuits in the same enclosure.