There are limitations of flux density saturation. In order to set a standard to rate all of the company’s materials and products, all the materials developed and in development are tested on a standard size toroid at 10 kHz. This allows engineers to develop a standard to rate the products for different applications. So, at higher frequencies, core saturation will shift and core loss becomes a larger constraint on design than flux density saturation. As seen here, Fair-Rite’s 79 material is limited to 1,500 gauss at 300 kHz before core loss becomes too great and goes into thermal shock.