When the Nike Free 4.0 launched in 2014—alongside the Free 3.0 Flyknit and Free 5.0—Nike hailed the models as the most significant evolution of Nike Free technology since its 2004 debut. Key innovations included a new outsole with hexagonal flex-groove patterns for multi-directional flexibility and a Flyknit upper that enabled the foot to move in all directions. On this December 2014 release, the knit upper is distinguished by a solid black base, accented with a blend of Poison Green and Total Orange hues.