It's a Size S0 unit, Class 10 trip curve, designed to mount directly onto a contactor — no separate enclosure needed for the motor starter assembly. The reusable packing ships in a pack of 88 units.
The 5.5...8 A setting range covers small three-phase motors in the 2.2 to 4 kW ballpark at 400 V. The 1NO+1NC auxiliary gives you a feedback signal for the PLC and a hard-wired shutdown path; the NO side reports the relay state, the NC side breaks the contactor coil circuit on a trip.
Deployment context
Snaps onto the matching S0 contactor (3RT2 series) on a DIN rail inside the motor control center.