Virtually Seamless™ toe 4 Degree® elite fit Indestructawool technology 8.5 overall crew height Merino wool blend fabric A high-quality, high-performance pair of socks from SmartWool. The SmartWool PhD Outdoor Light Crew Sock contains Indestructawool technology for incredible durability, and the 4 Degree™ elite fit system to keep the sock in place. Your feet will be dry and comfortable with mesh zones that provide ventilation.