D-curve and derating
The D characteristic means the magnetic trip fires at 10–20× In (30–60 A for this 3 A unit), so it won't nuisance-trip on the starting surge of a small motor or a transformer magnetizing inrush. At elevated panel temperatures, the thermal element derates: 2.76 A at 40 °C, 2.49 A at 50 °C, and 2.19 A at 60 °C — factor that into your continuous load if the breaker shares a crowded DIN rail.
Mounting and footprint
Mount in any position; IP20 with conductors connected. Combined top and bottom terminals simplify daisy-chaining busbars.