E cores derive from the classical cores made of silicon steel. The cross-section has specifically been developed so as to make the magnetic field within the core as homogenous as possible, with as much volume as possible for the coil. These cores are generally used for power converters and coils for switch mode power supplies. They are simple in shape. A disadvantage of the core is, however, that because of the rectangular cross-section of the center leg, coil winding, especially with large pieces of wire, is difficult. Because of its open structure, magnetic shielding is poor.