Infinity Challenge Zipper Compression Socks Zip design for easier on/off Open toe ideal for bunions or hammertoes Great for post-surgery Made with nylon and spandex,soft and comfortable Medium ankle circumference measures 8 1/2" - 10" and up to 16 1/2" Calf Circumference, Large 10" - 11 1/2" and up to 18", and X-Large 11 1/2" - 13" and up to 19". Calf measures are 8" above heel.