The Smartwool Performance Ski Targeted Cushion OTC is a performance merino blend sock with a thicker construction in the shin, heel and toe areas, offering extra protection and comfort. The rest of the sock uses a much lighter knit ensuring a good fit especially under tighter fitting boots. It also features 4 Degree Elite Fit System which uses two elastics for greater stretch and recovery so movement is kept free yet the sock will remain in place on your foot. Body-Mapped ventilation panels on the top of the foot prevent overheating retaining day long comfort inside a warm ski boot. Indestructawool Technology Indestrucatwool is a wool and yarn construction method used by Smartwool to create a wool and synthetic fibre blend which gives the best comfort and durabilty. 59% merino 38% nylon 3% elastane Smartwool Performance Ski Targeted Cushion OTC