This light and convenient Sorbothane Shock absorber for heel's absorbs 94.3% of impact shock (Nike Air is 55%) during exercise such as road work running. Slip into any of your running shoes, or general shoes while walking around, to help reduce injuries such as calf strain and achilles tendon injuries. Eases fatigue as well as discomfort after long periods of excercise.

Sizes:

Small = shoe size 3-5

Medium = shoe size 6-8

Large = shoe size 9-13