Smartwool Womens PhD Outdoor Light Micro Socks wool Light half-cushioned PhD Outdoor Micro stays in place, and is versatile for any sport. 73% Merino Wool, 25% nylon, 2% elastic. Washer and dryer friendly! Thanks to WOW Technology in high density impact zones, shock and abrasion are reduced. The 4-Degree Fit System keeps the sock in place. Women's sock sizes Small (shoe size 4-6.5) Medium (shoe size 7-9.5) Large (shoe size 10-12.5) NOTE Women's size Small fits Youth shoe size 2-4.5)