Tungsten, molybdenum, tantalum futhi niobium kukhona izinto ezibalulekile ukuze zezindiza kanye ukuzivikela izimboni ngenxa izakhiwo zabo: ephezulu lokushisa ukuzinza, ukuminyana futhi amandla eqine, machinability oncomekayo impahla, kanye nokuvikelwa ngemisebe.