To compare a couple of materials available, these curves show permeability verses flux density at 25ºC and 100ºC for both 67 and 78 materials. As shown here, permeability increases as magnetic flux increases to the ferrite's point of saturation and then starts to drop off. One of Fair-Rite’s lower permeability materials, 67, has an initial permeability of about 40 and increases to 180 at around 2,000 flux at 100ºC and begins to drop off. In comparison, a material with just over 50x 67’s initial permeability at 2,300 is 78, and at 100ºC it has a permeability of close to 8,000 before drop-off.