The Siemens 3RT7926-1CE00 is an RC surge suppressor designed to plug directly onto 3RT7 S0-frame contactors. It snubs the voltage spike when the coil de-energizes, protecting nearby electronics and extending contact life on inductive loads.
Snap it onto the contactor coil terminals — no wiring or separate DIN-rail bracket needed. The RC network is sized for the S0 coil's energy, so it matches the 3RT7 contactor family without derating or external resistors.
Out here in the grease, a snubber like this keeps the PLC input card from seeing a nasty voltage transient every time a motor starter drops out. If you've ever swapped a fried input module, you know the value of a couple bucks of RC protection.