Sold in a set of 4. A portion of the proceeds from Spitfire Wheels is directly donated to the San Francisco firefighters' toy program to support their ongoing work, including their skateboard day happening this December. Team-tested wheels by Spitfire. Formula 4 urethane for more speed, flatspot resistant, made of 100% high-quality urethane. Conical full shape with wider tread and conical sides for more control and speed everywhere. Ride the Fire! Cruise through the flames with Spitfire F4 Engine 29 Conical Full 99a Wheels. Formula Four urethane lasts longer, withstands heavier use, and outperforms all other wheels in performance. Designed to combine all desired characteristics of a high-performance wheel without sacrificing one feature for another. The Formula Four wheels are made from a 100% pure urethane blend and surpass all other wheels in performance and resistance to flats with less wear over time. Higher rebound for faster speeds on rough and smooth surfaces with a hard durometer for a smoother, faster ride that doesn't diminish over time. Designed with an exclusive anti-stick compound that allows for fast/even, smooth riding throughout.