The Siemens 5SL6125-7 is a 1-pole SENTRON miniature circuit breaker with a C tripping characteristic, rated 25 A at 230/400 V AC.
If your panel's prospective short-circuit current (PSCC) exceeds 6 kA, step up to the 10 kA variant in the same SENTRON family — the 5SL4 series — but the footprint (18 mm width per pole) and depth (76 mm) are identical, so no re-drilling. Single-pole switches only the phase; the neutral is either a solid busbar or a separate 2-pole device. Power loss of 2.6 W per pole at rated current in hot state matters for thermal coordination inside a crowded enclosure — 18 mm width leaves little air gap; derating per IEC 60898-1 table applies when ambient exceeds 30 °C or more than six breakers are ganged without spacing. Install inside a distribution board with at least IP3X enclosure rating.
One modular width (18 mm) per pole. The sealable feature allows a lead seal through the toggle slot for revenue-meter applications or tamper-proof zones. Halogen-free and silicon-free construction meets railway and marine material requirements where outgassing in a fire must be minimized.