The C-curve means magnetic trip at 5–10× In (100–200 A), so it's sized for inductive loads like small motors or fluorescent ballasts that pull a higher inrush. The 20 A rating covers 2.5 mm² copper circuits up to about 4.4 kW on a 230 V line. The arc-fault detection (–) handles series arcs as low as 2 A and parallel arcs up to 500 A — that's the full range of a glowing loose connection or a carbon-tracked cable.
At 18 mm wide, it takes one modular slot, so you can pack six of these per 108 mm of rail. Depth is 68.5 mm, installation depth 70 mm — leaves clearance for a standard 80 mm deep enclosure. Halogen-free and silicon-free if that matters for your spec.