The Siemens 5SU1653-7KV06 is a combined residual-current device and miniature circuit breaker (RCBO) — an FI/LS-protector Type A, rated at 6 A C-curve, 300 mA residual trip sensitivity, with a 4.5 kA breaking capacity in a 1+N-pole (single-pole switched neutral) package. The 70 mm width means it occupies two standard 35 mm DIN-rail module slots in the panel, which matters when you're packing a sub-distribution board and every slot counts.
The C-curve (6 A) trips magnetically between 5× and 10× rated current — so 30 A to 60 A instantaneous — making it a fit for motor-starter, lighting, or small-transformer circuits where inrush isn't extreme but isn't purely resistive. The 300 mA residual sensitivity (Type A) catches pulsating DC fault currents from single-phase rectifiers (common in washing machines, LED drivers, IT gear) while ignoring the normal leakage of a healthy installation. Type A is the minimum for circuits with electronic loads; Type AC would miss half the fault shapes. If your fault level is higher, you'll need to coordinate upstream with a larger MCB or fuse.