Set of replacement adjustment rings from Baratza for Baratza Virtuoso, Baratza Encore, Maestro Plus, Maestro and Baratza Starbucks Barista machines.
This three-piece set (adjustment ring, calibration ring, and locking screw) seats the coffee bean hopper, secures the ring grinder, activates the microswitch to turn on the motor, and serves to set and calibrate the grind.
See the following video for replacement instructions: