Waveguide Cover

Sharp Part Number : 252100100616 or 12570000001034

Dimensions: 106mm x 64mm
If your microwave is arcing or sparking during cooking, it may be that the waveguide cover is damaged. This metallic type material, which is a blend of mica and is invisible to microwaves, it covers the aperture that the microwaves pass through to get into the oven cavity. When old damp or contaminated can react to microwaves by arcing.  

Model this part fits:R-272WM