The Siemens 3RV2021-4DA15-Z W97 is a SIRIUS 3RV2 motor starter protector in size S0, rated for Class 10 overload protection with an A-release adjustable from 18 to 25 A and a magnetic N-release fixed at 325 A.
The screw terminal version (this one) is the panel-builder standard — no special tooling, accepts up to 16 mm² wire for the power circuit. The built-in 1 NO + 1 NC transverse auxiliary switch gives you a status feedback pair without adding a separate block; the NO feeds the PLC input for run status, the NC drops the holding circuit on a trip. Size S0 snaps onto a 45 mm wide DIN-rail footprint, so it fits a standard 600 mm wide enclosure with room for a contactor and terminal blocks alongside. Multi-unit packaging ships 12 units per pack — a line-down spare planner ordering for a bank of identical motor starters gets a single SKU for the whole row. The 97 x 45 x 90 mm dimensions mean each unit occupies about 0.4 liters of enclosure volume; factor that into your fill-factor calculation when laying out a multi-motor panel.