The Siemens 5SU1354-0KV25 is an FI/LS combination unit — an RCBO that packs both overcurrent protection and residual current detection into a single 70mm-wide module. It's a Type AC device rated for sinusoidal AC fault currents, with a 30mA trip threshold and 10kA breaking capacity. The B-curve 25A thermal-magnetic characteristic handles general-purpose and resistive loads without nuisance tripping on modest inrush.
The B-curve (3-5x In magnetic trip) is the right choice for lighting, socket outlets, and general-purpose circuits; if you're feeding motor or transformer loads with higher inrush, you'd want a C-curve instead.
Integration note
The 70mm width occupies three standard 18mm DIN-rail modules. It snaps onto the DIN rail without tools and the tunnel terminals accept up to 25mm² conductor — common for the 25A feed-through. The Type AC designation means it detects only sinusoidal AC residual currents; if your circuit includes variable-speed drives, UPS systems, or LED drivers that generate pulsed DC fault currents, you need a Type A or Type F device instead.