These bamboo socks are made from 94% bamboo fabric with 6% spandex for stretch.
Available in two infant sizes 3, and 4.
They come up to about mid to lower calf depending on sizing. 
 
I have personally been using these bamboo socks for more than seven years. It is recommended by the vendor socks are washed with similar fabrics. Possible pilling can been noticed with prolonged washing with rough textured fabrics (eg. zippered fabrics, jeans).