This general type of ferrite can be manufactured in several different vastly different grades by altering its composition and processing. Initial relative permeability (at 25 degrees Centigrade) can range from several hundred to twenty thousand. Saturation (at 25C) ranges from 3.5 to 5 kilogauss. The curie temperature can range from 100 to 300 degrees Centigrade. Material grades have been developed for particular groups of applications such as power, broadband, E.M.I./R.F.I. filtering, ripple filtering, tuning, and others. The useful frequency range for most of these materials is 1 megahertz and less (with suitable flux density de-rating), but some types approach 9 megahertz. Manganese Zinc ferrites have very low porosity.