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. 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