TDK / Epcos N27 material Manganese Zinc is used for low frequencies up to 100kHz, and EMI suppression up to 50MHz.  Commonly used for wide band RF transformers from 0.5 to 15MHz, ui=2000.  Refer to the N27 Material Data Sheet for more information.  Can be used in most applications in place of Fair-rite 77 material.