Spitfire formula four conical 101a skateboard wheels 54mma 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 54mm101a durometerflatspot resistancesmooth anti stick slide