This is a Siemens SIRIUS auxiliary switch block, order code 3RH2911-2HA02, designed to snap onto the front of 3RT2 contactors and 3RH2 contactor relays. It carries two normally-closed (NC) contacts, each rated for a maximum of 10 A, with the switching capacity derated by voltage — at 24 V it handles 6 A, at 110 V it handles 1 A, and at 400 V it handles 3 A. For AC-15 pilot-duty loads at 690 V it's rated 1 A. That means in a control panel you're using this to signal a 'stopped' or 'off' state back to the PLC or safety relay, not to break motor current directly.
Connections are spring-loaded terminals — no screwdriver needed for the wire, just strip and push. Accepts 2x (0.5 to 1.5 mm²) with ferrules, or 2x (0.5 to 2.5 mm²) bare stranded. That's a standard panel-building wire range; you'll be fine with 18 AWG or 16 AWG. Snap it onto the contactor front; the 36 mm width sits flush with the contactor body, so it doesn't steal extra DIN-rail space.
Insulation and protection
Mechanical life is rated at 10 million switching cycles, and contact reliability is 1 faulty switching per 100 million operations at 17 V, 1 mA — that's a good number for dry-circuit signaling where you can't afford a missed contact.