Coordinated sets rather than single spools — the reds, greens, golds, and metallics picked to work together, so you're not eyeballing whether a Christmas red from one line sits right next to a green from another. For most holiday projects a set covers the whole thing, and it costs less than assembling the same colors one spool at a time.
Sets here run from three-spool cotton and blendables packs up to twelve-spool tins and the Aurifil advent calendars. Weights range from 12wt for hand quilting and big-stitch work through 40wt for machine embroidery — check the weight against your project before ordering, since that matters more than the color choice does.