The MR21-0012-20 from MAST Technologies is a Microwave Absorber with Frequency 16 to 26 GHz, Thickness 0.010 Inch/0.25 mm, Thickness 0.010 Inch, Thickness (mm) 0.25 mm, Operating Temperature -60 Degrees F to 375 Degrees F. Tags: Cavity Resonance Absorber. More details for MR21-0012-20 can be seen below.