The EZ9F34140 is a 1-pole miniature circuit breaker from Schneider Electric's Easy9 range, rated 40 A with a C-curve trip characteristic. The 4.5 kA breaking capacity (Icn) at 230 V AC, conforming to IEC 60898-1, tells you it can safely interrupt a fault current up to that level without welding contacts or cascading upstream. That's the standard residential and light-commercial distribution rating; if your available fault current is higher, you'd need a breaker with a higher kA interrupt rating. The tunnel terminals accept up to 35 mm² rigid or 25 mm² flexible cable, which is generous for a 40 A device and makes it straightforward to land the feed conductors without a ferrule.
The 18 mm width and clip-on DIN-rail mount mean it occupies one modular position in a standard distribution board. The toggle actuator gives a clear visual indication of contact position — useful for lockout/tagout verification. The 66.5 mm depth leaves clearance for wiring ducts and cover panels in most enclosures.