The MR21-0004-20 from MAST Technologies is a Microwave Absorber with Frequency 6 to 11 GHz, Thickness 0.050 Inch/1.3 mm, Thickness 0.050 Inch, Thickness (mm) 1.3 mm, Operating Temperature -60 Degrees F to 375 Degrees F. Tags: Cavity Resonance Absorber. More details for MR21-0004-20 can be seen below.