The Spitfire Formula Four wheels are an excellent choice. The 99a durometer provides a smooth, controlled slide; sliding when you want them to and gripping when you need them to. It also helps when skating rougher terrain, providing the perfect balance of smoothness and slide-ability. This slimmer, classical shape provides a lot of speed and an easy slide. Recommended for skating street and a little bit of everything in between. Burn Fourever; and get lit with the Spitfire Formula four.