The MR21-0007-20 from MAST Technologies is a Microwave Absorber with Frequency 3 to 7 GHz, Thickness 0.08 Inch/1.8 mm, Thickness 0.08 Inch, Thickness (mm) 1.8 mm, Operating Temperature -60 Degrees F to 375 Degrees F. Tags: Cavity Resonance Absorber. More details for MR21-0007-20 can be seen below.