FRIO Cooling Bands were developed as a neat and effective way of controlling body temperature by cooling vital pulse points. The bands contain crystals activated by brief immersion in cold water, which then maintain their low temperature, even after hours of close contact with the body. These cooling bands can be worn around your neck or head and help you enjoy the advantage of staying cool while playing your favorite sport. Extremely helpful in reducing swollen ankles. Easily adjustable via a Cloth Tie fastener. Comfortable at all times. They work in the same way as the Frio wallets do and keep your ankles cool for hours. Medium: 11.5″- 12.5″**Please note: The above sizes are the dimensions of the band when activated including the velcro fastening. You will need to purchase bands that are approximately 1inch bigger than the circumference of you ankles. Sold in a Pair.