The Siemens 5SL4213-6 is a SENTRON miniature circuit breaker (MCB) — a 2-pole, B-curve device rated 13 A at 30 °C, with a 10 kA breaking capacity per both EN 60898 and IEC 60947-2 at 400 V AC.
Rated 13 A at 30 °C, but the thermal derating curve is published: 12.01 A at 40 °C, 11.44 A at 45 °C, 10.35 A at 55 °C. If your panel ambient runs at 40 °C, you're effectively working with a 12 A breaker — size up if the continuous load is right at 13 A. The 2-pole design (2 MW units, 36 mm wide) fits standard DIN-rail enclosures; depth is 76 mm (70 mm installation depth), so verify the enclosure depth if you're retrofitting into a shallow gland plate. Mounting position is any, which helps in tight layouts. IP20 with connected conductors — fine inside a panel, not for wet locations. Power loss per pole at rated current in hot state is 2.1 W; total 4.2 W for the 2-pole unit, a figure to factor into enclosure thermal calculations if you're packing multiple breakers in a small box.
Where it sits in the panel
Snap-on DIN-rail mount, 2 MW units wide (36 mm). The 50/60 Hz rating covers both mains frequencies globally.