Planar EE and EI Cores Fair-Rite Planar EE and EI Cores, with their low profile, are suitable for board-level installation allowing assembly without the need for plastic coilformers and can also allow windings integrated into multi-level PCB's. Planar ER Cores, with their low mass and low profile, are suitable for surface mount installations in power filter and transformer applications. Planar Cores can be supplied with the center post gaped to mechanical specifications as well as an AL value. Planar Cores are available in a range of sizes from EE14/7 to EE64/21, EI14/5 to EI64/15, and ER9.5 to ER14.5. They are available in 3 materials with Initial Permeability ranging from 2300 to 3000.