Content : The 2K12 "Kub" (Russian: 2К12 "Куб"; English: cube) mobile surface-to-air missile system is a Soviet low to medium-level air defence system designed to protect ground forces from air attack. "2К12" is the GRAU designation of the system. Kub is known in the west by its NATO reporting name "Gainful" as well as the US Department of Defense designation SA-6.