For magnetic material, there are different classes of materials that work best within a set range of frequencies. With metallic and powdered soft materials having high permeability, they are suited for the lower frequency range. Manganese-zinc and nickel-zinc are best suited for medium frequencies up to ultra-high frequencies in the 2 to 3 GHz range. Super-high frequencies are best matched with powdered iron cores for the microwave range up to about 30 GHz.