In 1987, Radick et al. discovered that Hyades stars are located on a diagonal sequence in a color-period diagram. Younger clusters have a more complex morphology, consisting of a similar sequence, called I, a faster C sequence, and some stars in the rotational gap, g, between them. The I stars spin down regularly, in a manner initially suggested by Skumanich, but the others are more complicated. I will begin with the observations, highlighting some recent results, and then go on to consider what these observations suggest for cool star spindown, including a new suggestion for identifying the underlying dependencies in stellar angular momentum loss, and formulating this spindown in a mathematically consistent manner for all of these stars.
