While the exact details of the Soyuz-M are not known, it is believed to be a two-stage rocket, derived from the Soyuz. It may have been similar to the later Soyuz-U. Following the cancellation of the Soyuz 7K-S, eight were launched with Zenit-4MT spacecraft. The first of these launches occurred on 27 December 1971, and the last on 31 March 1976. All launches occurred from the Plesetsk Cosmodrome, the first used Site 43/4, however the sites used by the subsequent launches were not recorded.