Nylon,Spandex TOP QUALITY: Formerly known as Microfiber Shades, the fibers in Microfiber Patterns are innovative in the sense that they enhance performance and durability. We use high-filament synthetics and channeled polyesters blended with cotton which wick away moisture. HIGH STANDARDS: All Sigvaris products are listed as Class 1(general edema) and Class 2(blood flow). Along with being ISO(International Organization for Standardization), this proves that our products truly benefit customers. ORIGIN: Born in Switzerland. Made in the USA. People buy and wear compression garments for the management of certain issues, such as leg comfort and management of DVT during long-distance travel and the management of leg swelling and vein issues. SIZING: Our knitting machines regulate stitch length and yarn tension while shaping the fabric to a leg model for the best fit. The compression level of these socks is 15-20mmHg, which was crafted with the most precise sizing chart in the industry.