The Osa class is the NATO reporting name for a group of fast attack craft developed for the Soviet Navy in the early 1960s. The Soviet designations are Project 205 (?????? 205) and Project 205U (?????? 205?) Tsunami. These craft are probably the most numerous class of missile boats ever built, with over 400 vessels constructed for both the Soviets and for export to allied countries. Two main variants were built: the Osa 1 (Project 205) which had box-shaped missile containers and the Osa 2 (205U) which had cylindrical missile containers. "Osa" means "wasp" in Russian, but it is not an official name.