The Schneider Electric A9KF21225BQ is a 2-pole miniature circuit breaker from the Acti9 K60 series, rated 25 A with a B-curve trip characteristic.
Rated breaking capacity is 10 kA Icn at 415 V AC, 50/60 Hz, per EN/IEC 60898-1. That's the standard domestic and light commercial fault level — enough for most final sub-circuits in a building distribution board. Limitation class 3 means it restricts let-through energy well, which helps with downstream coordination and reduces arc damage on a fault. If your panel has a higher prospective short-circuit current (say 16 kA or more at the main switchboard), you'd step up to a higher-rated MCB or an MCCB upstream.
Width is 36 mm (4 modules), so it takes four 9 mm pitches in the enclosure. Tunnel-type terminals accept 1…25 mm² rigid or 1…16 mm² flexible copper — strip 14 mm, torque to 2 N·m. IP20 rated, so it's for dry indoor enclosures only; no washdown rating. Operating altitude up to 2000 m, pollution degree 2, tropicalisation class 2 per IEC 60068-1 (handles 95 % RH at 55 °C).