The C11N3TM040L is a Schneider Electric ComPacT NSXm 3-pole moulded-case circuit breaker with a 40 A thermal-magnetic trip unit (TM-D) and a 50 kA interrupting capacity at 415 V AC — that 50 kA at 415 V is the performance level N rating, meaning it can safely clear a fault current up to 50,000 amps on a 415 V line without welding contacts or rupturing the case, which is the spec that decides whether this breaker coordinates with your upstream transformer or bus.
Backplate mount, 9 module pitches wide (81 mm), 137 mm tall, 80 mm deep — fits standard DIN-rail enclosures with a 35 mm pitch using spreaders, or 27 mm without. Front-front connection on both line and load sides, with Everlink lugs accepting 2.5–95 mm² rigid aluminium/copper or 2.5–70 mm² flexible copper — that's a wide wire range that covers everything from panel feeders to downstream tap conductors.
It's a standard catalogue item in the ComPacT NSXm family, so supply is steady through distribution channels.