Light, flexible, good ventilation of the foot, with enough support to run 3 times a week ... I am happy with this purchase, as with other versions of the Free series for this model .... the heel is slightly more firm and felt compared to fluorescent yellow model as well as the Nike Free 4.0 ... Free 4.0 became my street shoes and I run with also occasionally ... but I run most often with 5.0. Black Fluo ... as the advantage with black, this model is that the sole recovers less gravel than fluorescent yellow ....