The ABB XT1NU3125AFF00NXXX is a 3-pole molded case circuit breaker from the XT1N series, carrying a 125 A frame and a TMF 125-1250 thermal-magnetic trip unit. The description confirms UL/CSA listing, so it is built for North American panel builds where a UL 489 or CSA C22.2 No. 5 breaker is required on the BOM. The TMF trip gives a fixed thermal and magnetic setting — no interchangeable rating plugs, which simplifies ordering but locks the protection curve to the 125-1250 A range.
The 125 A frame on the XT1N body means this breaker fits into the standard XT1 panel footprint — same width, depth, and mounting hole pattern as other XT1N units. The TMF 125-1250 trip unit covers a wide magnetic pickup range (1250 A is 10x the 125 A frame rating), which suits motor-starting inrush or high-peak loads where a lower magnetic setting would nuisance trip. The 3-pole configuration with F F (fixed front terminals, front connection) keeps wiring consistent across the switchboard; no lug kit to order separately.