The latest member to join the spitfire team polar39s own hjalte halberga true performance conical shape hand cut for quick response and less weightall spitfire wheels are hand poured shaped and specifically engineered in san francisco ca usaonly the most advanced formulas and compounds are used for all wheelswe achieve the highest levels in tolerance and true speedfeaturesformula four performance urethaneset of 4 wheelsdiameter 52mm99d durometerflatspot resistancesmooth anti stic