This variable is the stand alone prescription drug plan (PDP) or Medicare Advantage Prescription Drug (MA-PD) region name in which the plan benefit package provides coverage. Applies only to stand-alone PDP's and regional Medicare.
The code number associated with this region name can be found in the variable called (REGION_CODE).
The CCW constructs the Plan Characteristics File from information submitted by Part D plan sponsors to CMS's Health Plan Management System (HPMS).
Source: CMS (HPMS Files)