What it is and where it mounts
The ABB 1SAZ721201R1053 is a thermal overload heater from the Thermal Overload Heaters for Starters line, set to an adjustable current range of 29-35 A. It drops into the matching ABB overload relay base alongside a contactor to give a motor-starter its running-overcurrent trip curve — the heater element is what carries and senses the motor load current, so the dial setting has to match the motor's full-load amps on the nameplate.
Rating that drives the BOM line
The 29-35 A adjustable range is the single functional rating on the record for this code, and it's the one that decides fit — a motor pulling inside that window under normal service will trip on sustained overload but ride through the inrush.