The Siemens 5SL3301-7 is a SENTRON miniature circuit breaker (MCB) — a 3-pole, C-curve unit rated 1 A at 400 V AC, with a breaking capacity of 4.5 kA per EN 60898 and 5 kA per IEC 60947-2.
At 30 °C ambient it carries the full 1 A; derate to 0.95 A at 40 °C, 0.92 A at 45 °C, and 0.87 A at 55 °C, so if your enclosure runs hot, factor the thermal curve into the load calculation. Rated for 400 V AC phase-to-phase with a maximum of 440 V AC in multi-phase operation. The 4.5 kA breaking capacity under EN 60898 covers most residential and light commercial fault levels; the 5 kA rating per IEC 60947-2 gives a bit more headroom for industrial panel coordination studies. Depth is 76 mm, width 54 mm (3 modular units), installation depth 70 mm.