The Eaton XT5HU340AMFF000XXX is a 400 A, 3-pole motor circuit protector (MCP) from the XT5H series, carrying both UL and CSA approvals. The 400 A frame size tells you it's sized for the heavy end of the motor lineup, not the little fractional-horsepower stuff.
The 3-pole configuration covers three-phase motor loads. UL and CSA listing means it's accepted in North American panels without a separate fuse block or supplementary protection debate; the inspector sees the mark and moves on. The XT5H series is a compact frame for this current class, so panel fill factor is better than older generation MCPs that needed more DIN rail real estate.