Nike Shox R4 Transparent Fundus is a series of Nike Shox R4 shoes. It is designed by Nike with Shox technology. From the pictures of the Nike Shox R4 Transparent Fundus, you‘ll notice that there are four Shox columns in the heel, produced from a unique, highly resilient formula that is also used in Formula One racing cars. They are designed to collapse efficiently to control impact; quickly at first, then slowing the foot before returning to their original height through the energy stored in them, helping to propel the foot through the footstrike motion. This is quite noticeable, as my foot felt a responsive spring whenever I started to strike the heel down on the ground. They are also equally spaced around the center of the calcaneus (a tarsal bone in the heel) to give a trampoline style response at the point-of-peak rear foot pressure, thus the spring. These columns also vary from each size, engineered across the size range to produce a unique feel for all sizes and body weights. This is like the filling of the sandwich.