The Siemens 3RT2926-4NA00 is a SIRIUS adapter in size S0, designed to mount auxiliary switch blocks of the 3RH29..-…..-0MC0 type onto a contactor. It's the mechanical interface that lets you add signalling contacts to a S0 contactor frame — no wiring changes, just snap the adapter on and clip the switch block in.
The adapter is sized for the S0 contactor frame. It snaps onto the contactor front, then the auxiliary switch block (3RH29..-…..-0MC0) clips into the adapter. No tools, no panel rework — it's a field-add solution that takes about as long as swapping a terminal block. The titanium grey finish matches the SIRIUS contactor line, so the panel stays visually consistent.