Rotation rate (﹩v\mathrm{sin}\,i﹩, in km s﹩^{-1}﹩) vs. dereddened B−V for solar‐type stars in four clusters. The upper line is meant to schematically outline the upper bound to rotation for the Pleiades. The lower line is a mean relation for the Hyades from Paper IV. (a) The Pleiades, 100 Myr old, from Paper IV. The triangles represent upper limits to ﹩v\mathrm{sin}\,i﹩. (b) NGC 6475, 220 Myr old, from James & Jeffries (1997). (c) M34, at 250 Myr. There are four stars in the Pleiades and five in M34 that exhibit Hα emission that rises above the continuum, and their points are overlaid with crosses. (d) the Hyades, at 600 Myr. For the Hyades, the open symbols represent ﹩v\mathrm{sin}\,i﹩ values, while the filled symbols are determined from observations of rotation periods, and so have no aspect dependence.