It's a panel-mount disconnect or branch-circuit protector sized for distribution and motor-control center applications where a compact, 3-pole footprint is needed. The 3-pole configuration means it switches all three phases simultaneously — standard for three-phase motor loads, feeders, and sub-distribution panels. The TMF trip unit provides thermal overload and magnetic short-circuit protection in one package.
The closest functional peer is the XT1NU3090AFF000XXX, also a 3-pole XT1N frame but rated at 90 A instead of the 125 A TMF rating of this unit. The physical footprint and mounting pattern are identical — both share the XT1N frame — so a panel designed for one can accept the other without rewiring, provided the ampacity and trip curve match the load requirements.
The 3-pole block occupies a single modular width; plan for adequate bending radius on the incoming and outgoing conductors to avoid stress on the line-side terminals.