The Siemens 5SV3342-6KL is a 4-pole Type A residual current circuit breaker (RCCB) from the SENTRON family, rated 25 A with 30 mA sensitivity at 400 V AC, 50 Hz. It is an instantaneous device — no intentional delay — so it trips on the first half-cycle of a ground fault, which is the right call for general-purpose protection where selectivity with downstream devices isn't the priority.
The 30 mA trip threshold is the standard for personnel protection in most residential and commercial panels. The 4-pole construction (N left) means the neutral is switched and monitored, so it suits 3-phase + N systems where you need to detect leakage on any phase or the neutral. Rated short-circuit current is 10 kA per IEC 61008-1, with a conditional short-circuit rating of 0.8 kA — enough for typical sub-distribution boards but verify against your prospective fault current if you're close to the transformer.
Mounts on DIN rail (REG) in any position.