The Os1St Performance Foot Sleeve helps relieves symptoms of plantar fasciitis, Achilles tendonitis, heel pain, foot swelling, and other discomforts. This sports foot compression sleeve will support the muscles while you work hard and are comfortable and easy to wear daily. The high-performance design delivers six different zones of compression. The support sleeve can be worn under socks and inside shoes or overnight for relief from morning pain. Worn as a pair, during your run or sport, FS6® functions as strengthening support and Plantar Fasciitis preventative. One pair per pack. Medium fits men's shoe size 6 to 9½ or women's size 7 to 10½. Size large fits men's 10 to 13. Refer to the size chart before ordering.