If you had to have only one pair of socks, look no further. Quick drying and durable, these socks act as thermostats by cooling or heating when needed. The reinforced heel and toes increase comfort and durability, while the arch support increases circulation and decreases foot fatigue. Designed to avoid blisters, these socks will take you from a snowy mountain hunt to a Death Valley hike. Fits: Mens shoe sizes: Medium(5-8), Large(9-12), X-Large(13-15) Womens shoe sizes: Small(4-7), Medium(8-9), Large(10-11)