The Siemens SIRIUS 3RT5956-1CC00 is an RC-element surge suppressor for contactor coils and relays. Rated for AC/DC control supply voltage, it covers 70 to 150 VDC and 48 to 127 VAC at 50 Hz, with the same AC range at 60 Hz.
This is a bolt-on accessory for SIRIUS contactors and relays — it mounts directly onto the coil terminals, typically snapping into the front of the device. No separate DIN-rail footprint is consumed, which matters when the panel is already tight on fill factor. The RC element is polarity-sensitive on DC circuits; verify the orientation against the coil's + and - before energizing.