It mounts directly onto the contactor, protecting the coil and control circuit from inductive kickback that can damage PLC outputs or cause nuisance faults.
This part is listed as a phased-out product. The official successor is the SIRIUS 3RT2 series surge suppressor. The multi-unit packaging (10 units per pack) means you may need to buy a full sleeve even if you only need one.
The suppressor snaps onto the contactor's coil terminals — no wiring changes needed if the contactor already has the mating slot. It is sized for the S00 frame (45 mm wide, 57.5 mm tall, 72 mm deep), so it fits the same DIN-rail footprint as the base contactor. The 240-400 V AC rating covers common control voltages across European and North American panels.