The 3640-300 from Holland Shielding Systems is a Microwave Absorber with Absorption 25 to 50 dB, Frequency 30 MHz to 110 GHz, Power 1.5 kW, Thickness 11.81 Inch/300 mm, Thickness 11.81 Inch. Tags: Ferrite, Pyramid, Foam Absorber. More details for 3640-300 can be seen below.