Four main classes of commercial molybdenum-base alloys exist. The most common of the carbide-strengthened alloys is known as TZM. Other alloys in this class include TZC (1.2% titanium, 0.3% zirconium, 0.1% carbon), MHC (1.2% hafnium, 0.05% carbon), and ZHM (1.2% hafnium, 0.4% zirconium, 0.12% carbon).