The MR21-0001-20 from MAST Technologies is a Microwave Absorber with Frequency 14 to 18 GHz, Thickness 0.02 Inch/0.5 mm, Thickness 0.02 Inch, Thickness (mm) 0.5 mm, Operating Temperature -60 Degrees F to 375 Degrees F. Tags: Cavity Resonance Absorber. More details for MR21-0001-20 can be seen below.