Fox River Mills Pioneer Medium Weight Crew Sock 33% Merino wool, 33% acrylic, 32% nylon, 2% spandex. Memory-knit construction holds form, wash after wash. Contoured rib top holds sock in place to eliminate slippage. Spandex compression zones add support and keep sock in place all day long. Vented panels remove moisture and keep feet dry. Reinforced toe and heel add comfort and extend sock life.