The Siemens SENTRON 5SL6306-6RC is a 3-pole miniature circuit breaker rated 6 A with a B tripping characteristic and a 7.5 kA breaking capacity tested to EN 60898. The B curve means the magnetic trip activates between 3 and 5 times rated current (18–30 A for this 6 A unit). That's a good fit for resistive and general loads; if you're feeding motor or transformer inrush you'd normally reach for a C curve instead.
Rated 6 A at both AC and 30 °C ambient, so no derating guesswork for standard panel conditions. Multi-phase operation is rated at 440 V AC maximum, single-phase at 250 V AC. DC rating maxes out at 72 V — useful for control circuits but not for high-voltage DC bus protection.