Are these good for running or the gym?

They are lightweight and moisture wicking, but the thin polyester knit has no cushioning or arch support. They work better for casual wear and short workouts than for long runs.

Will the print fade or crack in the wash?

The care label calls for a cold machine wash at 30C or below, no bleach, no iron and no dry cleaning, and drying flat. Following that keeps the print and the spandex blend in better shape.

How do I pick the right size?

Sizing is given as length by width: S is 33 cm by 10 cm, M is 39 cm by 10 cm and L is 41 cm by 10 cm. Match the length to your foot and lower leg rather than to a shoe size.

Do they stay up on the calf?

The spandex blend gives stretch, and the mid-calf height gives more fabric to hold than an ankle sock. The knit is thin, so very active wearers may find them looser than ribbed sport socks.

No. They are 90% polyester and 10% spandex, which is what gives the moisture wicking and the stretch. Expect a smoother, less absorbent feel than cotton socks.