A note from the designer:
Gauge is important to the fit of this sock. A 3x1 rib knit on a bias is not as stretchy as when knit straight, so keep that in mind when choosing yarn and needles. The socks pictured in the pattern were knit with Panda Superwash (186 yds/50 gms) on US1 needles. They’re size Medium and fit my size 8 feet.
So if you’re planning making OI with a thinner yarn and/or smaller needles, or if you’re going to work M1 increases instead of yo’s, consider making a larger size.
Outside In is worked entirely inside out, so the majority of stitches are worked as knit stitches. When the sock is finished, turn it right side out (or should that be outside in?), and voila!, the ribs become spines on a field of purl stitches with sweet columns of eyelets down the center front and back.
A gusset provides more room for the instep. As an added bonus, reversing the sock gives you a fabric suitable for any Princess and the Pea, with the smooth side of the stockinette pampering your sole.