The A9KF21220BQ is a Schneider Electric Acti9 K60 miniature circuit breaker — a 20 A, 2-pole unit with a B-curve trip characteristic, rated to interrupt 10,000 A Icn at 415 V AC per EN/IEC 60898-1. It's a thermal-magnetic breaker with a magnetic tripping threshold of 3 to 5 times In, so it's sized for general-purpose distribution where the inrush isn't extreme — lighting, small motor circuits, resistive loads. The 2 protected poles mean a single device disconnects both line and neutral in a single-phase or split-phase panel.
That's a standard 2-pole MCB footprint; no surprises in a populated enclosure. Depth is 70 mm, height 81 mm.
Standards and environmental
Designed to EN/IEC 60898-1 for overcurrent protection in household and similar installations. Suitability for isolation is confirmed to that standard. Pollution degree 2, overvoltage category II. Operating altitude 0 to 2000 m. Electrical and mechanical durability both rated at 20,000 cycles.