Power Inductive EER Cores Fair-Rite Power Inductive EER Cores have been designed to make optimum use of a given volume of ferrite material for maximum throughput power. The structure, which includes a round center post, approaches a nearly uniform cross-sectional area throughout the core and provides a winding area that minimizes winding losses. EER Cores can be supplied with the center post gapped to mechanical specifications as well as an AL value. Fair-Rite Power Inductive EER Cores are available in a range of sizes from EER25.5/18 to EER49/54 and three materials with initial permeability ranging from 2300 to 3000.