The D-curve (10–20× In magnetic trip) is sized for high-inrush loads — small transformers, solenoid banks, motor starters. At 1 A rating, it protects the wiring to a control transformer or a PLC power supply, not a motor branch circuit.
For a buyer filling a BOM line, the 5SY4401-8CV is a straightforward spec-in: the 15 kA Icu at 400 V matches what most European-style panel designs expect from a high-breaking-capacity MCB in a 4-pole D1 configuration.
Snap-on DIN-rail mounting per EN 60715. The 4-pole body occupies four modular pitches (72 mm at 18 mm per pole). Terminal capacity accepts up to 25 mm² conductor — sufficient for the 1 A rating, but the lug size is set by the 15 kA breaking capacity, not the load current. Verify the busbar comb matches the 4-pole spacing if feeding from a common supply.