Grey with Birds Bamboo Socks featuring 7-11 UK, 40-45 EU, 9-12 US sizing are 80% Bamboo Fiber, 17% Polyamide, and 3% Elastane. These super soft, anti-bacterial socks have reinforced heels and toes and contain more bamboo than many other brands. Additionally, the recycled cardboard label is a testament to Joya's commitment to sustainability, and the socks are best washed at 40 degrees and not tumble dried.