Its 1.25 A rated operational current at AC-3 (400 V) and 690 V rated insulation voltage suit it for small motor loads or control transformers in 400 V three-phase panels. The 16 A instantaneous magnetic short-circuit trip responds fast enough to protect downstream contactors and cabling.
The 45 mm width and 96 mm depth fit standard 45 mm-wide DIN slots; the S00 frame leaves clearance for adjacent components. Any mounting position is permitted. Screw-type terminals on top and bottom accept 2x (0.75 to 2.5 mm²) solid or stranded, or 2x 4 mm² — torque to 0.8 to 1.2 N·m. Clearance requirements: 50 mm above and below, 30 mm at the sides, zero forward or backward.
Sourcing note
The part is genuine Siemens SIRIUS — same part, different passport, as I say. No warranty geofencing concerns on this standard catalog item.