Free pattern (link goes directly to .pdf at web.archive.org)

Gauge note: No gauge is listed on the pattern itself and apparently the gauge is not listed on the ball band of the recommended yarn. On Knitter's Review for the yarn, the gauge range is listed as: 7 to 8 stitches per inch on US 1-3 needles

Summary: Socks with no toe or heel, knit in the round

Description from pattern: These nifty socks are prefect for chilly Pilates (or Yoga) workouts. They let you grip the mat with openings for your heels and toes, while keeping the rest of your feet snug.