The Birkenstock Cotton Slub Sock Black brags about the high level of soft and skin-friendly cotton. The casual cotton sock features a fit enhanced by the pliant cuff and flat toe section. Long-lasting comfort and optimum protection are provided by the reinforced toe and heel sections. The sock is elasticated and includes a pressure-free cuff. The sock is comprised of 94% cotton, 4% polyamide, and 2% spandex.