Snaps onto standard DIN rail, so it integrates into any 35 mm rail-based enclosure without extra hardware.
Compared to the 3-pole S203-D13 (10 A, Curve D), the S204-C25 adds a fourth pole for neutral protection and doubles the current headroom. The D-curve sibling handles higher inrush (welder, transformer) but at a lower ampacity; the C-curve here is the better fit for general-purpose lighting and motor branch circuits where you need the full 25 A.
DIN-rail footprint means it clips into a 4-module-wide slot in any 35 mm rail panel. The 25 A rating typically feeds a subpanel or a group of lighting circuits; watch the thermal derating if you pack adjacent breakers at full load in a sealed enclosure.