Nike recently released the latest edition of its Free 4.0 Flyknit trainer. More flexible than the 5.0 and more cushioned than the 3.0, the newest addition features a lightweight, supportive one-piece Flyknit upper made entirely of polyester yarn, and a highly flexible, low-profile outsole. The heel mimics the shape of the foot, rolling with the ground to promote a more natural footstrike. New hexagonal flex grooves are cut into the outsole and wrap around the sidewall so your foot moves more naturally in every direction. Secondary cuts intersect the flex grooves, adding even more flexibility. The new Nike Free 4.0 Flyknit is now available online for $120 USD.