The Siemens 5SV4445-0 is a 4-pole residual current operated circuit breaker (RCCB), Type AC, rated 125 A with a 100 mA trip sensitivity on a 400 V AC supply. The 100 mA sensitivity is a common choice for fire protection and equipment protection in industrial panels; it's less sensitive than the 30 mA required for personal shock protection, so it's typically used downstream of a 30 mA RCCB or on circuits where nuisance tripping from leakage is a concern. The 4-pole configuration covers three-phase plus neutral, making it a fit for three-phase loads like motor starters, heating banks, or general power distribution where earth-fault protection is needed on all poles.
The product class is B: return restricted — contact your Siemens partner for returns or warranty issues. This is a standard restriction for Siemens circuit protection products; it doesn't affect normal procurement.