As with previous models, the upper is made of Flyknit, a special fabric that Nike created sometime in 2012. But what is specific about this model? That a new kind of knit was created, Knitposite. Heat-treated/cured Flyknit. This Knitposite is used on the back of the shoe at the 17th, to guarantee the stability and strength of the heel and ankle in it. Of course, it is also mixed with an ordinary Flyknit, which is located at the top.