E Cores Fair-Rite E Core geometry offers an economical design approach for inductive applications in a variety of power designs. Fair-Rite E Cores can be supplied with the center post gapped to mechanical specifications as well as an AL value. E Cores are available in a range of sizes from EF 12.6 to E 65/27 and 3 materials with Initial Permeability ranging from 2300 to 3000.