Sizes - Child med/lge & Adult sm/med/lge

The masculine rib pattern on the leg and instep of these socks alternates single knit stitches with 2 purl stitches and 2 seed stitches. The purl stitches tend to recede to make the panels of seed stitch more prominent. This type of rib doesn’t draw in as much as tradition knit 1, purl 1 or knit 2, purl 2 ribs, but it has sufficient elasticity for a snug fit.

~ From Getting Started Knitting Socks, pg 88