With suppression materials, there is a wide range of materials with varying permeability. Fair-Rite’s highest permeability material is the 75 material shown here in red at 5,000 perm., and not shown with a permeability of 10,000 is the 76 material, which is good for a frequency range of 1 kHz to 11 MHz. The lower permeability materials cover the rest of the range of frequencies up to about 3 GHz. Fair-Rite’s 31 material is ideal for 1 to 300 MHz, and the 61 and 67 materials are good for noise suppression from 200 MHz to 3 GHz.