GO:0000924

A centrosome-localized multiprotein complex composed of gamma-tubulin and other non-tubulin proteins assembled into a ring structure that is thought to be the unit of nucleation at the minus end of a microtubule. Gamma-tubulin small complexes are thought to be the core repeating units of the ring. [GOC:clt, GOC:mtg_sensu, PMID:12134075, PMID:17021256]