What this MCB does on the rail
The Schneider Electric EZ9F26125 is a 1-pole Easy9 miniature circuit breaker rated 25 A with a B-curve trip characteristic (magnetic release between 3 and 5 times In).
B-curve trip — what it means on the line
Curve B trips magnetically at 3 to 5 times rated current (75 to 125 A for this 25 A unit). That's a fast trip on short-circuit but a higher threshold than curve C (5–10× In). If you're feeding motorized loads or transformers with a higher inrush, a curve C or D would be a better fit; the B curve would nuisance-trip on the starting surge.
DIN-rail fit and panel space
Width is 18 mm — one modular pitch on a standard DIN-rail enclosure. Height 81 mm, depth 66.5 mm. Clip-on mounting; no tools needed to snap it onto the rail. The tunnel terminals accept 1 to 25 mm² rigid or 1 to 16 mm² flexible cable, torqued to 2 N·m. That's enough lug capacity for a 25 A feed in 4 mm² or 6 mm², but the 2 N·m spec means you're not cranking down hard — use a torque screwdriver, not feel. IP20 finger-safe front; fine inside a closed distribution board, not for wet locations.