75 ( J ) material Manganese Zinc is a high permeability ferrite that is used for wideband transformers and EMI suppression from 0.15 to 10MHz.  75 Material is very similar to TDK T65 ( ui=5200 ), and J material ( ui=5000 ).  Refer to the 75 Material Data Sheet for more information. 

Check the range of T65 material cores for other sizes not stocked in a 75 material.