What you're sourcing
The ABB 1SAZ331201R1006 is a thermal overload heater for starters, catalogued under Contactors and Starters within the Circuit Breakers, Fuses and Protection family. It is the heater element that pairs with the matching ABB thermal overload relay base — the heater sets the motor full-load amp trip window the relay enforces.
Where this class lives in the panel
Thermal overload heaters like this one mount directly to the ABB thermal overload relay that drives the contactor coil — heater installs on the relay, relay is wired downstream of the contactor. The heater's current rating is what determines the motor FLA window it will protect; swap the heater to retune the starter for a different motor without replacing the contactor or relay base. ABB's 1SAZ heater family is the heater-side companion to the thermal overload relay in the same catalogue branch. On a starter assembly the relay is the reusable part; the heater is the application-specific part that gets pulled when the motor on that bucket changes.
Sourcing posture
Spec it into the BOM by exact order code 1SAZ331201R1006; no production-status entry is on file, so lifecycle is not asserted. It is quoted to order against an RFQ — drop the MPN and quantity on the request for availability and lead time against the live distributor network.