Nike is back with the latest version of its 4.0 Flyknit trainer featuring a number of updates. With more flexibility than the 5.0 and more cushion than the 3.0, the latest 4.0 version is sure to perform. The upper is constructed of a one-piece layer of polyester yarn providing an ultra contoured fit and lightweight support, while the mere 6mm difference between the inner sole and ground allows for a more natural feel. Furthermore the new hexagonal flex grooves have been hot knife-cut into the outsole and wrap around the sidewall allowing your foot to move more naturally in each direction. The Nike Free 4.0 Flyknit is available at the Nike online store for $120 USD.