On Running Ultralight Mid Sock Mens. Ideal for running. XL (US 11.5 – 12.5) I think worn once (if at all!) and washed. Immaculate condition. Material: 38% polyester (recycled) 58% polyamide (recycled) 4% elastane. "Featuring extra comfortable performance fabric that keeps your feet feeling fresh and supported mile after mile. Perfect for enhancing your athletic experience with superior fit and functionality."