On June 20, the International Atomic Energy Agency (IAEA) reported that Iran is preparing to enrich uranium using the second of two advanced IR-6 centrifuge cascades at the underground Fordow facility. This second cascade is the first to feature modified sub-headers that enable it to easily pivot between different levels of uranium enrichment. Iran has not told the IAEA the level at which the new cascade would enrich uranium but had given previous estimates of 5 to 20 percent purity.