Curve K is the middle ground between B and C curves — it trips magnetically at 8 to 12 times rated current. That makes it a good fit for inductive loads like small motors, transformers, and solenoid valves that draw a brief inrush without nuisance-tripping. At 2 A, this breaker handles motor loads up to roughly 0.5 kW on a 230 V line, or smaller control transformers. The thermal element handles the overload protection; the magnetic element clears the short.
Single-pole width (roughly 17.5 mm per module) means it takes up one slot in the panel. No special busbar or adapter needed for a standard ABB S200-series distribution board.