Crystal structure "white tin" respectively. Two more allotropes, γ and σ, exist at temperatures above 161 °C and pressures above several GPa. White tin is metallic, and is the stable crystalline form at or above room temperature. Below 13.2 °C, tin exists in the gray form, which has a diamond cubic crystal structure, similar to diamond, silicon or germanium. Gray tin has no metallic properties at all, is a dull gray powdery material, and has few uses, other than a few specialized semiconductor applications. Although the α–β transformation temperature of tin is nominally 13.2 °C, impurities (e.g. Al, Zn, etc.) lower the
Arena Naucalpan 15th Anniversary Show Anniversary Show is the fourth oldest still ongoing annual show in professional wrestling, the only annual shows that older are the Consejo Mundial de Lucha Libre Anniversary Shows (started in 1934), the Arena Coliseo Anniversary Show (first held in 1943), and the "Aniversario de Arena México" (first held in 1957). The Arena Naucalpan 15th Anniversary Show was organized by Alfonso Moreno and featured a large number of wrestlers from Consejo Mundial de Lucha Libre (CMLL), who allowed Moreno to book their wrestlers on a regular basis and in this case also sanctioned a match for the CMLL World Middleweight Championship.