Graduated compression makes the OS1st Fleet Feet Performance Calf Sleeves ideal for any activity. The medical-grade compression can help alleviate common overuse conditions, like Achilles tendonitis, shin splints, leg cramps and aching muscles, but it also improves circulation, supports muscles and stabilizes tendons. Like the OS1st AS6 Arm Sleeves, each calf sleeve employs six zones of compression. Starting from the bottom of the sleeve near the ankle, OS1st uses light compression to stabilize your Achilles tendon. Moving up the calf, zones two and three use firm compression to boost circulation and support important ligaments. Zones four and five have moderate compression for stabilize your calf muscle and continue to aid circulation. And the top of the sleeve, in zone six, uses light compression for a comfortable fit. OS1st knits the calf sleeves from soft, moisture-wicking fabrics to give you the most comfortable fit possible. The Fleet Feet version comes in black with blue and white stripes and a Fleet Feet logo to show off at your next group run. For the best fit, measure around your leg at the ankle (the narrowest part of your leg) and the middle of the calf (the widest), then match the circumferences to the size in the chart below.