The Siemens 3RH1911-1MA20-ZW98 is an auxiliary switch block carrying two normally open (2NO) contacts, designed for snap-on mounting alongside SIRIUS contactors and motor starters in a control panel.
Snap-on mounting to the right side of a 3RT2 contactor or 3RA2 starter — no tools required for installation, and the 2NO configuration provides isolated feedback contacts for PLC inputs or status indication.