The Skyline crew Sock by Fox River is lightweight and made to stand up to any adventure. Made from sustainable fibers of TENCEL and Merino wool, they'll keep you warm and dry. Fox River's proprietary Helix Fit System offers an unmatched fit with full-foot volumetric compression.>A Y-shaped gore at the heel creates more cross stretch and non-binding flex at the ankle, while also creating a more defined pocket for your heel to sit snug.