This is a Siemens SIRIUS power contactor, designated 3RT1016-1MB41-0KT0, in the compact S00 frame size. The S00 frame keeps the footprint tight at 45 mm wide, 57.5 mm tall, and 72 mm deep, so it fits neatly on a 35 mm DIN rail per EN 50022, with side-by-side mounting possible at a 6 mm spacing. The IP20 rating on the front and terminals means it's finger-safe inside an enclosure, not meant for washdown — this one lives in a dry panel.
The key number for a sourcing buyer is the AC-3 rating: 4.5 kW at 400 V. That's the motor-starting duty — switching a standard three-phase induction motor on and off under load. The S00 frame handles that current comfortably. That's a tougher service, so if your application does frequent reversing, this is the figure to watch. The coil is a DC-operated unit, pulling 1.4 W to close and 1.4 W to hold. That's a low, steady draw — no AC hum, and it plays well with 24 VDC control supplies common in PLC cabinets. Wire sizes: the screw terminals accept 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²), and up to 2x (0.75 to 4 mm²) for the main contacts. AWG equivalents are 2x (20 to 16) or 2x (18 to 14), and a single 12 AWG.
For Type 1 coordination (contactor may need replacement after a fault), it's a 35 A gL/gG.