Waveguide Cover 

Part number: FCOVPA022WRK0
Dimensioins;112 mm x 121 mm
Supplied as a pack of 2 
Suitable for : Sharp R8000 Series Microwave Ovens 

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.