Why Ferrite is a ceramic made by sintering iron oxide with other metal oxides such as nickel, zinc or manganese, and the exact recipe, called the mix, sets the material's permeability and loss characteristics versus frequency. A high permeability manganese-zinc mix (like mix 31 or 75) works well at low HF for common-mode chokes, while lower permeability nickel-zinc mixes (like 43 or 61) are chosen for upper HF and VHF. Choosing the wrong mix can make a choke nearly useless or cause it to overheat, so catalogs list a recommended frequency range for each mix number.
Watch out Physical dimensions such as thickness or the diameter ratio affect how much inductance a given core produces and how much power it can handle, but they do not change the frequency range where the material is effective.
Ferrite mix number = frequency range. Low mix numbers like 31 for low HF, 43/61 for higher bands.