The 40 A rated current at AC tells you this RCCB can carry 40 A continuously on each pole without overheating — sized for a 3-phase load up to roughly 27 kVA at 400 V line-to-line. The 300 mA residual tripping threshold is higher than the typical 30 mA personal-protection level; it's intended for equipment protection or fire-prevention on circuits where nuisance tripping from normal leakage (long cable runs, industrial loads) would be a problem. Terminal cross-section accepts solid or stranded conductors from 1.5 to 25 mm², with a tightening torque range of 2.5 to 3 N·m — standard for screw-type terminals in this class. Rated surge current resistance of 1 kA (8/20 µs waveform) means it can withstand typical lightning-induced surges without damage, provided the upstream overcurrent device limits let-through energy.
This RCCB is a panel-mounted residual current protection device for 3-phase 400 V AC distribution in commercial and industrial buildings — think lighting panels, small machine feeds, HVAC equipment, or general sub-distribution boards. For those, you'd need a type A or type B RCCB. The finger and back-of-hand safe protection against electrical shock (per the evidence) confirms the live parts are shielded when the device is installed — a basic safety requirement for accessible panel components.