Relative stoichiometry of Shs1 and Cdc11 modulates septin ring diameter. Shs1-containing complexes (S) were mixed with increasing amounts of Cdc11-containing complexes (C) in high salt in the ratios indicated. The resulting mixtures were diluted into low salt buffer and then examined in the EM. (A) Shs1-containing complex alone; mean outer ring diameter of 410 ± 53 nm (n = 109). (B) 9:1 ratio; mean outer ring diameter of 608 ± 86 nm (n = 80). (C) 5:1 ratio; mean outer ring diameter of 692 ± 92 nm (n = 48 nm); (D) 3:1 ratio; mean outer ring diameter of 846 ± 141 nm (n = 44). (E) 1:1 ratio; no rings. (F) Cdc11-containing complex alone. (G) Values obtained in A–D plotted as a histogram. Error bars are the standard deviations.