Anatomically designed to provide advanced plantar fascia and arch support, the Vectr Cushion 1/4 Crew Sock leverages a unique X-LOCK support system to lock the foot in place and reduce blistering for your most comfortable run ever. Product details ANTI-BLISTER X-LOCK technology provides advanced arch and plantar fascia support and locks the foot in place within the sock to reduce blistering CUSHION 3.25mm maximum cushioning to deliver ultimate shock absorption during forefoot impact, push-off and heel impact ANATOMICAL DESIGN Engineered to conform to left and right structure of the foot for better fit WIDE TOE BOX Seamless wide toe box eliminates a key irritation point and promotes natural toe splay improving balance, alignment and comfort QUICK-DRYING Moisture wicking yarns and zoned mesh ventilation areas keep your feet cool and dry FABRIC COMPOSITION 88% NYLON, 12% LYCRA COMPRESSION RATING MODERATE: 15-20 mmhg at base of foot SIZING: SMALL: US MEN 3.5-5.5 US WOMEN: 5-7 MEDIUM: US MEN 6-8 US WOMEN: 7.5-9.5 LARGE: US MEN 90-12 US WOMEN: 10-13