Miele Microwave Grill retaining nut - 07993200In order to gain access to the mica waveguide cover in the roof of the oven you would need to unscrew the knurled nut that holds up the grill element. The nut corrodes in time and it may be easier to replace it once removed. This 6mm knurled nut is suitable for many Miele models of microwave and combination ovens. Manufacturers part number Models include : H5030BM, H4012BM, H4050BM, H5080BM, H4010BM, H7640BM, H77640BM, H4082BM, H7840BMX, H7840BMX,