Jump Soles - Small (Sizes 5-7) provided by JDVCommerce - Versatile high-density rubber platforms work to stretch and strengthen the Achilles tendon and calf muscles. Developing muscle resiliency in the area is vital to explosive leg power. Jump Soles will blast your lower legs like nothing else you ve ever tried. After training with Jump Soles you ll run faster jump higher and change direction quicker. Simple hook and loop strap on. Also includes detailed training manual and video.