The Siemens 3RV6311-1GC10 is a SIRIUS circuit breaker sized S00, designed specifically for starter combinations — meaning it integrates the motor-protective and short-circuit functions into one device ahead of a contactor. Rated 6.3 A at AC-3 (400 V) and 690 V insulation class, it's the branch-circuit protector for a motor load up to that current. The magnetic short-circuit trip responds at 82 A instantaneous, so it clears a bolted fault before the contactor welds shut.
That 96 mm depth means it sits flush with most 100 mm deep enclosures; you're not fighting the gland plate. Screw-type terminals on top and bottom accept 2x 0.75–2.5 mm² solid/stranded or 2x 4 mm², torque to 0.8–1.2 N·m.
The 82 A instantaneous magnetic trip means it rides through motor inrush (typically 6–8x FLA for a few cycles) and only opens on a hard short. Rated operational frequency maxes at 15 operations per hour at AC-3, so this isn't for a rapid-cycling application like a stamping press; it's sized for a pump, fan, or conveyor start every few minutes. Power loss is 6 W typical — negligible in a ventilated enclosure, but worth noting if you're packing a dozen of these in a sealed box.