Pack of two mica waveguide covers.

Part number:12570000001034, asw.,D839846, 252100100616

Dimensions (including tabs) approx 116 mm x 64 mm
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.  

Fits models:R-272KM, R-272SLM, R-272WM, R-372.