Stirrer Blade Cover WP4359963

Appearently, food splaters and cleaning corroded and/or removed the metalized film on original part, causing the arching (of ions, I think). Two plastic push pins are all that hold disk in place. Since microwave worked w/o part I decided to replace only the part (rather than the entire microwave). Push pins come apart easily and are re-used to secure new 9" disk. Simply pry gently under the round, broad, and flat pin head to release pin. Push pins are tiny and consist of two parts: a male center pin and a female grummet-like round part with a center hole. When the pin is seated it puts pressure in all directions (laterally) in the grummet. Because the disk is light weight, this is sufficient to hold disk in place.
Having a picture of the original part (cover-stir disk), on scaled gragh paper made it easy to calculate size and be assured that this was the correct part. Even Sears didn't have a clear drawing or photo of their replacement part. Kudos to PartsSelect. I much preferred buying a $50. part over $250. to replace and landfill the unit. Also, the name Cover-Stir (or Stir-Cover), relates to the part function with ventilation.