The Siemens 3VU2931-4A is a release detector with a single changeover NO/NC contact, designed for integration with the 3VU2.4 and 3VU2.5 series. It mounts directly onto those motor starter protectors, providing a remote signal when the overload release trips — a critical spare for any panel running 3VU2-based motor branches.
For a maintenance-spares purchaser, this is the kind of part you want one of in the cabinet before a motor branch trips and the panel doesn't report it. The changeover contact gives a positive NO/NC indication back to the PLC or annunciator — no spare, no sleep if the line depends on that signal.