Siemens SENTRON 5SY6306-6CC — 6 A B-Curve MCB, 3-Pole
Breaking capacity is 6 kA per EN 60898 and 5 kA per UL 1077 / CSA C22.2 No. 235. That 6 kA rating covers the vast majority of residential and light commercial panel applications in IEC territories; the 5 kA UL figure means it's accepted in North American branch circuits listed under UL 1077 (supplementary protectors).
The 6 A rating holds at 35 °C ambient. Above that, the thermal element derates: 5.51 A at 40 °C, 5.25 A at 45 °C, 4.97 A at 50 °C, and 4.69 A at 55 °C. The operating temperature range is -40 °C to 75 °C, with humidity limits that step down as temperature rises — up to 95% RH at 55 °C, 55% at 70 °C, and 35% at 75 °C. That covers outdoor enclosures in cold climates and hot attic spaces alike. The IP20 rating (with conductors connected) is standard for a DIN-rail device inside a closed enclosure; it's not meant for washdown environments.
Dimensions are 54 mm wide (3 MW), 90 mm tall, and 76 mm deep. Installation depth is 70 mm.