The Siemens 5SY4120-7CC is a SENTRON miniature circuit breaker rated 20 A at 35 °C with a C tripping characteristic and a 10 kA breaking capacity per EN 60898. This 1-pole unit fits a single 18 mm modular width slot on a DIN rail, making it a standard fast-mover for branch-circuit protection in control panels and distribution boards.
At 20 A, the 5SY4120-7CC handles 20 A continuously at 35 °C; at 40 °C it derates to 18.38 A, at 50 °C to 16.58 A, and at 55 °C to 15.62 A. If your panel runs hot, size accordingly.
Snap-on mounting to a DIN rail, any position, 18 mm wide (1 modular width unit). The quick-assembly fastening method and combined top/bottom terminals mean you can bus-bar multiple units without extra adapters.