Formula four is the wheel of choice for many skateboarders since its release. It is available in 99a and 101a. Both are hard, with the 101a being about exactly as hard as I would want a wheel when skating smooth spots. I prefer the 101a on concrete and asphalt because it felt faster than the 99a.  How does it compare to any other wheel? It's good, it's actually really good. Try both the 101a and the 99a at some point. Both formulas are really good. There was no problem sliding with both either hardness, and I didn’t get flat spots. Compared to the Bones STF wheels, I would say the two formulas on both on the same level, just different. My suggestion is that Formula Four is kind of like the VX of wheels. Is kind of yellow, works well and it’s not broke don't fix it.

Our product description for Spitfire Formula Four

Unmatched flatspot resistance

Smooth anti-stick slide

High rebound compound

100% true performance urethane skateboard wheels.