The Siemens 5SJ6125-7RC is a 1-pole SENTRON miniature circuit breaker (MCB) rated 25 A at 240 V AC with a C tripping characteristic and a 6 kA breaking capacity per EN 60898.
Where it fits — panel and environment
The 18 mm width (1 MW) means it takes up the same slot as any single-pole MCB — no extra space needed. IP20 with connected conductors, so it belongs inside a closed panel or distribution board, not in a wet or dusty location.
The closest functional peer is the 5SY4125-7CV, also a 1-pole 25 A C-curve MCB in the same 18 mm footprint. The 5SY is built to IEC/EN 60947-2 and carries a 15 kA breaking capacity — more than double the 5SJ's 6 kA (EN 60898). The 5SY also has a higher pollution degree (3 vs 2) and is rated for mechanical engineering/industry environments, while the 5SJ is tagged for retail-line use. If your panel requires a higher fault-current rating or a more robust industrial spec, the 5SY4125-7CV is the direct upgrade. For standard residential or light commercial distribution where 6 kA is sufficient, the 5SJ6125-7RC is the correct fit.
Halogen-free and silicon-free construction, sealable for tamper-proofing. Mechanical service life of 10,000 switching cycles typical.