The Siemens 5SL7125-7RC is a Betagard miniature circuit breaker — one pole, C-curve trip characteristic, rated 25 A at 30 °C. The C-curve means it holds through mild inrush — think motor starters, contactor coils, or a bank of relays — and trips fast on a short circuit. Breaking capacity is 15 kA per EN 60898 and 20 kA per IEC 60947-2, so it handles a stiff fault on a 240 V AC single-phase or 440 V AC three-phase line without welding its contacts shut.
Derating and ambient realities
That 25 A rating holds only at 30 °C. At 40 °C it's 23.75 A; at 50 °C it drops to 22.5 A; at 60 °C it's 21.5 A. The breaker can mount in any position, so it tucks into tight gland-plate layouts without worrying about orientation.
Width is 18 mm (one modular unit), depth 76 mm, height 90 mm. Installation depth is 70 mm — leaves room behind the DIN rail for wiring.