The Dynamic Fit system is made up of 'fingers' of soft material that wrap the midfoot and arch, tailoring the shoe perfectly to your foot. For added support and comfort, the molded sockliner mimics the foot's curvature. Flex grooves along the length and width of the outsole enhance flexibility and help maintain stability for a more natural stride. For added flexibility and to help increase foot strength, the Nike Free Run+ 3 also has diagonal cuts through the arch area. The upper offers lightweight support right where you need it, with seamless overlays for a supportive, skin-like fit. Reflective Swoosh design trademark for enhanced visibility in low light Nike+ ready