Nike Free 4.0 Flyknit

With its sleek, lightweight and flexible design the Nike Free 4.0 Flyknit features a few interesting and needed updates from the Free Run series, including the Flyknit upper and new outsole.

The shoe offers a 6mm drop, which provides a closer ground to foot contact, and is considered an intermediate in the Free Run series (more cushion than the 3.0 and more flexibility than the 5.0).

Sitting at $120 a pair, the 4.0 Flyknit seems like an affordable and necessary addition to your shoe arsenal.


Nike Free 4.0 Flyknit Upper

Inspired by barefoot running, the Free Runs are a product of eight years of research in insole pressure to create a shoe that mocks being bare foot. While staying true the Free Runs’ roots, the 4.0 Flyknit takes the goals of the series to the next level. In combination with a shoe that feels like being barefoot and weights around 8 ounces, the Flyknit addition, which is also based on years of research, imitates the soft, snug feeling of a sock.

In comparison to the original Flyknit+, which was so narrow and tight that it forced the toe-box into a curve, the 4.0 Flyknit contours to the foot beautifully. The upper, or Flyknit, is made completely of polyester yarn that molds seamlessly to foot. The sock-like material, that includes an attached tongue, allows your feet to move and stretch freely while offering support in needing areas.

Though still fitting snug from the heel to mid-foot and implementing a non-stretchy material in the heel for additional support, the updated shoe fits more naturally and is true to size. Unlike the previous version, the toe-box allows your toes to splay comfortably and naturally. The material also allows you to pick and chose when you’d like to wear socks. Additionally, the lacing, which is asymmetrical, minimizes the possibility of pressure point formations.

Nike Free 4.0 Flyknit Sole

The lower midsole, which is made of Phylite, complements the original Free Run ideals by remaining true to its barefoot running roots. The blown rubber material is flexible and soft, but tough enough to be used as an out-sole. Thus, to further cut down on weight and firmness, the 4.0’s outsole is made predominately of exposed Phylite midsole. Nike includes rubber pads on only the big toe and heel, allowing the midsole to make up 90% of the outsole.

Additionally, Nike gushes that impact is absorbed by the waffle-like outsole lugs. The minimal use of rubber keeps the weight down and allows the shoe to flex and move more naturally. Though using Phylite as both the midsole and the majority of the out-sole keeps the shoe light and pliable, it does little for durability and traction. The Phylite foam actually strips off layers as you run.

Nike managed to hit the nail on the head when designing a shoe that mocked the normal movements of the foot. The upper contours beautifully, imitating a comfortable sock feel, and the outsole and lower work together to create a natural run feel.


As mentioned above, the Nike Free Run 4.0 Flyknit shoes are a desirable addition to most athletes (some of Kenya’s most renown runners own and love these shoes) who like to switch things up between several different types of shoes, and at $120 a pop they are definitely not breaking the bank. What the 4.0 shoe may lack in durability it makes up in comfort, cushion, flexibility and fit.

However, because of its certain and steady breakdown over time, we encourage backups with different strengths. This shoe is not a one size fits all, but it does have welcomed updates from the v3 version.