Combining Nike Free flexibility with the engineered support and breathability of Nike Flyknit technology, the Nike Free 4.0 Flyknit is a conglomerate of comfort. Flyknit construction gives you stretch and support where you need it most. Dynamic, supportive fit through the midfoot with Flywire technology in the laces. Flyknit tongue with notches that creates easy on and off. Knit heel with non-stretch material, so your structure stays firm while you stay supported. Low-profile Phylite™ midsole offers a resilient ride, and is tough enough to double as an outsole, which reduces overall weight to the shoe. Hexagonal flex grooves offer six different flex points for natural range of motion, with secondary cuts that intersect the hexagons for even more flexibility. Minimalistic, molded sockliner mimics the curvature of the foot for added support. Anatomical heel on the outsole is rounded, offering more natural range of motion as it rolls with the ground. Traction and durability with.