The Formula Four Classic Wheel from Spitfire features Unmatched Flatspot Resistance Smooth Anti-Stick Slide High Rebound Compound Classic Shape Set Of Four Buy Spitfire Formula Four Skateboard Wheels at Native Skate Store. Formulated to give you a harder faster ride the 101 Duro Formula Four Wheels from Spitfire feature unmatched flatspot resistance, smooth anti-stick slide, high rebound compound and are shaped to last longer. Tested by the Spitfire team, Formula Four are their best skateboard wheel yet. The 101D Classic Wheels are 56mm in diameter and a Classic shape. All our skateboard wheels are sold as a set of four.