Wheels made for compulsory exercises are manufactured through injection of a unique Hytrel-Dupont material. The special features of this wheel include its profile and its finish. Available in two diameters (60 and 63) and in four varieties of hardness: 50 D soft - for slippery surfaces 54 D medium - for fairly slippery surfaces 58 D medium hard -for regular surfaces 61 D hard - for rough surfaces.. The narrower profile and the smooth surface guarantee greater manoeuvrability and easy skating.