The Siemens SIRIUS 3RT1326-1AB00 is a 4-pole power contactor in the S0 frame size, rated for 40 A at 40 °C ambient and 11 kW at 400 V in AC-2 and AC-3 duty — that's the motor-switching rating you care about for pumps, conveyors, or compressors. It carries four normally-open main contacts (no NC on the main poles) and uses screw-type terminals on both the main and auxiliary circuits, so it's a straightforward swap into an existing panel without crimping special connectors.
Side-by-side mounting is allowed (no derating gap needed), which saves rail space in a crowded enclosure. Dimensions are 85 mm high, 61 mm wide, 91 mm deep — the depth matters for shallow back-panel enclosures where you're squeezing in a row of contactors and overloads.