The ECO Explore/Travel Crew sock is your most versatile sock for seeing the sites on your "Once in a Lifetime Vacation" or going to the office! The perfect combination of eco-friendly sustainability while amazingly soft, breathable and durable - keeping you comfortable, and blister-free. Over 3.5 plastic bottles used in each pair of socks REPREVE® Recycled Polyester inner and outer layers Stabilizer Zone™ in arch locks sock in place High needle count for added durability Certified, Sustainable and Blister-Free socks - No Blisters, Guaranteed! Fiber ContentInner Layer: 70% Repreve® Polyester, 26% Nylon, 4% Lycra®Outer Layer: 68% Repreve® Polyester, 24% Nylon, 8% Lycra®