Uses original Vanathane technology. 57 mm diameter; black and white; precision bearing style only. Sure-Grip groups it in the hard category, below the hardest Fo-Mac family. Compression-molded Fo-Mac formulas differ from modern urethane and differ from one another. Sure-Grip says floor material, skater weight, temperature and other conditions affect performance. Fo-Mac products should not be assigned an invented urethane A durometer. The current manufacturer page does not specify the sold pack quantity. Confirm quantity with Diamond before ordering. Photos show an example variant. Select your size or color where offered; confirm stock with Diamond.