The Siemens 3RH2911-4GA40 is a SIRIUS auxiliary switch block designed to snap onto the front of a 3RH2140 or 3RH2440 contactor relay (size S00). It gives you four normally-open instantaneous contacts, rated 10 A at AC-12 (resistive) and 6 A at 24 V for typical control loads. The ring terminal lug connection means you're landing ring lugs, not ferrules — plan the panel wiring accordingly.
Snap-on mounting directly onto the contactor relay — no DIN rail required, no extra bracket. The block is 36 mm wide, 43.7 mm deep, and 37.5 mm tall, so it tucks into the S00 footprint without stealing panel space. IP00 on the front means it's not sealed; keep it inside a clean, dry enclosure away from washdown or dust.
The AC-12 rating (10 A) covers resistive loads like pilot lights and contactor coils. For inductive control circuits (AC-15), the switch is good for 1 A at 690 V. The DC ratings are more modest: 6 A at 24 V, 2 A at 48 V, 1 A at 110 V, and 0.3 A at 250 V. If you're switching a DC solenoid at 125 V, the 0.9 A limit is the one to watch.
What it is not
This switch is not a mirror contact per IEC 60947-4-1, so it cannot serve as a feedback contact for a safety circuit that requires mirror contacts. It has no leading or lagging contact — all four NO contacts close and open together.