Ride with precision on Spitfire's Formula 4 Classic 99a Wheels, incorporating classic design with high-performance, long-lasting urethane. Unparalleled in flatspot resistance, these wheels provide a smooth, fast ride and remain consistent with an anti-stick compound. Formula Four urethane and a hard durometer deliver more speed and control, lasting longer with less wear than all other wheels. Get the best of both worlds - higher rebound for faster speeds plus longer shape retention. So go ahead - KEEP THE UNDERGROUND LIT.