Since teenagers often grow out of their shoes so quickly,they often throw away shoes which are quite new. FitFeet sneakers can expand to fit your feet while they are getting longer and longer. At the time you put your feet into FitFeet, they will stretch to proper size of your feet. Therefore you don’t have to worry about growing out of your shoes. The special structure of the sole can only be produced by 3D printer. By 3D printing,it costs less time and material waste.