The 3640-50 from Holland Shielding Systems is a Microwave Absorber with Absorption 30 to 50 dB, Frequency 30 MHz to 110 GHz, Power 1.5 kW, Thickness 1.96 Inch/50 mm, Thickness 1.96 Inch. Tags: Ferrite, Pyramid, Foam Absorber. More details for 3640-50 can be seen below.