The Bircham is the original Sealskinz sock. With a durable surface material, pleasant Merino liner and a waterproof, breathable Aquasealz membrane in between, they're ready for hiking, cycling, trail running and many other sports. Thanks to the liner material, this model is right at home in cool conditions. - Outer: 62% polycolon polyester, 29% polyamide, 9% elastane - Aquasealz membrane inside the structure - Lining: 36% merino wool, 36% acrylic, 18% polyester, 5% polyamide, 5% elastane - Made in the United Kingdom. Size letter, UK size, Euro size and compatible foot length range: - S= 3 - 5 UK / 36 - 38 Euro / 22cm - 23.7cm - M = 6 - 8 UK/ 39 - 42 Euro / 24.6cm - 26.2cm - L = 9 - 11 UK / 43 - 46 / 27.1cm - 28.8cm - XL = 12 - 14 / 47 - 49 / 29.6cm - 31.3cm