Fracture toughness refers to the material's ability to withstand cracking caused by a shock wave crossing it. Ceramics with low elasticity (high Young’s Modulus), compared to metals, for example, do not offer high resistance to mechanical shocks. There is, however, a type of ceramic preferred for applications where the user requires flexural strength in addition to other mechanical properties: zirconium oxide (or zirconia), and, in particular, Y-TZP zirconia (yttria-stabilised zirconia) or ATZ. To a lesser extent, silicon nitride, alumina-toughened zirconia or certain alumina may also be used.