The SIRIUS 3RT1916-1CB00-ZX90 is an RC surge suppressor — a plug-on snubber for contactor coils. It handles 24...48 V AC and 24...70 V DC, so it fits the common control-voltage range across European and North American panels. The RC element absorbs the inductive kick when the coil de-energizes, which keeps transients off the PLC output and extends contactor life.
Packaged as a multi-unit lot of 10 — that's how it ships from Siemens, so a single order code gets you a strip of suppressors for a bank of contactors. It plugs directly onto the coil terminals of SIRIUS 3RT contactors; no wiring change, no DIN-rail space consumed. For a panel builder, that means one line item covers a whole row of contactor suppression.