The Siemens 5SU1653-6KV06 is an FI/LS-Protector Type A (PSE/SSF) — a combined residual current device (RCD) and miniature circuit breaker (MCB) in a single 1+N-pole unit. It carries a B-curve 6A overcurrent trip and a 300mA residual current sensitivity, with a 4.5kA breaking capacity. The 70mm width means it occupies two standard modular DIN spaces in a distribution board.
The 4.5kA breaking capacity (Icn) is the short-circuit withstand rating per EN 61009; it safely interrupts faults up to that level without upstream damage, provided the prospective short-circuit current at the installation point does not exceed 4.5kA.