This specification deals with soft magnetic manganese zinc ferrite core materials for high frequency power transformer and filter inductor applications. Standard types of both power transformer and filter inductor material are defined. For power transformer use, there are five types defined by their maximum core loss density and minimum saturation flux density. For filter inductor materials, three types are defined based on their inductance permeability. Apart from magnetic property requirements, dimensional tolerances and workmanship requirements are defined in this specification.