RollerBones Art Elite 101A Competition Roller Skate Wheels (Set of 8) Roller bones team wheels have proven competition shapes poured in a high rebound, easy to ride, medium hard, long-lasting formula This technology costs a little more but if you need the ultimate in roll, grip and wear, this is the wheel for you This material was developed by Roller bones & introduced in the early 1990's It has been copied but not duplicated, making this wheel & urethane unique