- Size: 32/33 • Self-heating tourmaline thermal socks to keep warm. • Material: High-quality tourmaline and polyester cotton. • Color: Black. • One size fits most men and women. • Keep feet warm in cold climates. • Suitable for outdoor activities such as climbing, skiing, fishing, jogging, hunting, cycling, and hiking. • Relieve fatigue and promote blood circulation. • The package includes 4 pairs of self-heating socks. • The correct way to wear the socks is that the self-heating point should be in contact with the soles of the feet.